205
P A R T I
T H E T R I B E S T IP E A E
1 . 1 . His t o r y
T he tribe Stipeae was described by N ees von Esenbeck (1829, p. 371) based on the genus Stipa L. and including Chaetaria, o f w hich he considered Aristida to be a synonym . In Stipa, Nees included Oryzopsis, Piptatherum an d Urachne as synonym s. F o u r years later K u n th (1833, p. 187) enlarged the trib e by including Streptachne but redivided the com prehensive genus Stipa sensu Nees in to five g e n e ra : Stipa,
Lasia-grostis, Macrocldoa, Oryzopsis an d Piptatherum . T rinius & R uprecht (1842, pp. 1
& 97) still fu rth er enlarged the concept o f the tribe by including Diclielachne a n d
Anisopogon. They divided Stipa into five sections an d regarded Urachne a n d
Lasia-grostis as distinct genera, each w ith tw o sections; in ad d itio n , Aristel/a a n d
Ortho-raphium were upheld as genera distinct fro m Stipa. F u rth e r additions were m ade
by Bentham (1882) an d this tendency culm inated in H ackel’s treatm en t o f the trib e (1896, p. 100-104). H ere twelve genera were included alth o u g h m any genera form erly recognized were relegated to synonym y an d thus a very wide concept o f S tipa was reintroduced. In conform ity w ith the recent tren d o f dividing the grasses in to sm aller, m ore “ n a tu ral ” tribes, m ost present-day a u th o rs have again severely restricted the n u m b er o f genera included in the Stipeae. In the in tro d u ctio n to his m o n o g ra p h o f A ristida, H enrard (1929, p. 13), sum m arized his concept o f the Stipeae in a key to the genera nam ely Stipa, O ryzopsis, Nasella, Piptochaetium, Aciachne, M ilium , Aristida an d Timouria. H ubbard (1934, p. 214) treated the trib e essentially in th e sam e m anner, but did not m ention Timouria (ap p aren tly including it in Stipa).
A vdulov (1931, p. 406) in his classic w ork on the karyosystem atics o f the G ram in ea e pointed o u t th a t the genera Stipa an d O ryzopsis are m ore closely allied to genera such as Phaenosperma, O ryza an d Ehrharta th a n to the genera o f the tribe Agrosteae in w hich they are placed by som e au th o rs. H e cam e to this conclusion m ainly, n o t only on the basis o f karyological sim ilarity, viz. sm all chrom osom es w ith basic n u m b er 12, but also on the basis o f the presence o f certain prim itive features exhibited by th e florets, e.g. 3 lodicules in O ryza a n d S tip a, a n d 6 stam ens in Phaenosperma, O ryza
a n d Ehrharta. A natom ically the leaf-blades o f these genera also show a great deal o f sim ilarity. A vdulov pointed o u t, how ever, th a t the genera p robably evolved independently a n d thus represent d istin ct evolutionary groups.
T he fact th a t Aristida occupied an an o m alo u s position in the Stipeae was realized by H u b b a rd (H u b b a rd & V aughan, 1940, p. 23) w ho rem oved this genus from th e
Stipeae to accom m odate it in his new tribe, th e Aristideae. (L atin diagnosis published by H u b b ard in Bor, 1960, p. 685). E ight years later H u b b a rd (1948, p. 325) tra n sferred
M ilium from the Stipeae to the A grosteae, b u t did n o t list the genera to be re ta in e d in the Stipeae since only British grasses were dealt w ith in the relevant w ork.
A n im p o rtan t, th o u g h lesser k n ow n, w ork on the Stipeae, is th a t o f Elias (1942). His w ork is unique in the Gramineae in th a t he m ade a com parative study o f th e fo ssil a n d living form s o f the Stipeae a n d by this m eth o d w as able to indicate certain ev o lu tio n a ry trends o f the tribe. In o rd er to enable him to com pare fossil rem ains w ith living species o f Stipa, Oryzopsis, Piptochaetium and Nasella, Elias m ade a th o ro u g h study o f the m orphological characteristics o f th e “ h u lls ” o f these grasses. W here possible he subdivided the genera in to sections, each section being com posed o f a g ro u p o f closely related species. In ad d itio n to the fo u r genera m entioned a b o v e , Elias devoted several pages to a discussion o f the relationship o f Stipa to A ristida
o th e r genera u n d er consideration. H e stated th a t Aristida p ro b ab ly evolved from
Stipidium (a fossil genus) th ro u g h Stipa, sum m ing up his views as follow s: “ The
com prehensive m o d em genera Stipa a n d A ristida o f Stipeae, w hich betw een them selves differ prim arily in the division o f the single stro n g awn o f Stipa in to three slender aw ns in Aristida, are ap p aren tly descendants o f a single fossil genus Stipidium w ith a n o n -in d u rated awn ” . T he reasons w hy th e present a u th o r ca n n o t su p p o rt Elias’s views will be elaborated u n d er the discussion o f the relationship o f Aristida to Stipa,
as seen in the light o f recent advances in the know ledge o f their an ato m y , karyology a n d em bryology.
P arodi & Freier (1945), w ho studied the Stipeae b o th anatom ically a n d taxonom i- cally, include Aristida, as a distinct n atu ra l genus, in the Stipeae. F u rth erm o re they reg ard the genera Stipa, Nasella a n d Oryzopsis to be so closely related th a t the possibility o f accom m odating th em to g eth er as tax a o f infrageneric ra n k can n o t be precluded. Aciachne is regarded n o t to be a close relative o f the foregoing an d the view is expressed th a t it p ro b a b ly represents a distinct subtribe o f the Stipeae w hereas th e taxonom ic position o f M ilium an d Relchella in relation to the above is n o t yet clear.
In a recent account o f the Stipeae, R oshevitz (1951) divided the tribe in to three su b trib es and included Streptachne an d Am phipogon, as well as resuscitating several genera such as Lasiagrostis, M acrochloa, Orthoraphium, Timouria a n d Ptilagrostis
w hich are placed in synonym y u n d er Stipa by m ost present-day w orkers. O n account o f the existence o f a large n u m b e r o f species som ew hat interm ediate in c h arac ter m ost o f these genera are do u b tfu lly distinct from Stipa. In ad dition Amphipogon and
Streptachne could be placed m ore satisfactorily in other tribes. T heir taxonom ic
position will be discussed in the course o f this paper.
T he m ost recent account o f the tribe is th a t o f Pilger (1954, p. 330-332) w ho again included Dichelachne, M ilium a n d Aciachne, recently rem oved from the tribe by o th er au th o rs. His reason for do in g so was p ro b ab ly m otivated by a d istrust o f the present-day tendency to over-em phasize the taxonom ic value o f an ato m ical features o f the vegetative organs th u s to som e extent under-estim ating the im p o rtan ce o f the m orphology an d internal stru ctu re o f the reproductive organs. Pilger’s classification consequently is m ore artificial th a n one w ould have expected, i.e. if all d a ta available h ad been evaluated in determ ining relationships. Finally a new genus o f the Stipeae,
Trikeraia, based on Stipa hookeri Stapf, w as described by Bor (1954, p. 555).
1 .2 . De l im it a t io n
207
T he follow ing genera were, a t som e tim e o r o ther, included in the Stipeae; they all, how ever, possess certain c h aracters w hich do n o t co n fo rm to those o f th e typical representatives o f the tribe a n d have therefore been excluded.
M ilium .— (H e n rard , 1929; B entham , 1882; D arlin g to n & Wylie, 1955; H u b b a rd , 1959; H ackel, 1896). Lem m as aw nless, chrom osom es in m ultiples o f 4, 9 o r 14 a n d m u ch larger th an in the Stipeae. P ro b ab ly — as d one by H u b b a rd (1948)— best placed in the Agrosteae on account o f the large chrom osom es.
Aciachne.— (H en rard , 1929; B entham , 1882; H u b b a rd , 1959; H ackel, 1896).
O n m orphological and anatom ical g ro u n d s regarded as p ro b ab ly representing a su b trib e o f the Stipeae (P arodi & Freier, 1945). T his genus is in need o f fu rth er investigation.
M uehlenbergia, Lycurus, Perieilem a.— (H ackel, 1896); spikelets 1- or 2-flow ered;
glum es persistent, shorter th a n the lem m as; lem m as 3-nerved, practically aw nless; hilum punctiform an d basal in M uehlenbergia a n d Perieilema and p ro b ab ly likewise
in Lycurus (no fruiting m aterial seen); em bryo as in the Paniceae except fo r th e
em bryonic leaf (i.e. sheathed by th e coleoptile) w hich has the m argins overlap p in g (R eeder, 1957); chlorenchym a o f the leaf-blade radially arran g ed ro u n d the bundles (A vdulov, 1931; Schwabe, 1949); two-celled epiderm al hairs recorded for M uehlen
bergia and Lycurus (T ateoka, 1959); chrom osom es sm all, in m ultiples o f 8, 10 o r 14
(D arlington & Wylie, 1955). D arlington & Wylie (1955) place M uehlenbergia a n d
Lycurus in the Sporoboleae, while R eeder (1957) places them in the
Chloridoid-Eragrostoid group (which includes Sporobolus), m ainly on the characters o f the em bryo.
Pilger (1954) places all three genera in the trib e Eragrosteae; Perieilema an d Lycurus
in the subtribe Lycurinae, and M uehlenbergia in the subtribe Muehlenbergiae. Schw abe (1949) likewise suggests th a t Lycurus a n d M uehlenbergia should be placed in t h e
Eragrosteae. On the available evidence this seems an excellent way o f expressing
th eir affinities.
Brachyelytrum.— (B entham , 1882; H ackel, 1896). R hachilla produced b e yond
the base o f the floret; grains flattened an d grooved ventrally; em bryo “ festucoid ” except for the cleft present between th e base o f the scutellum and the c o le o rrh iz a; chrom osom es always in m ultiples o f 11. Placed by Pilger in the Festuceae. R eeder (1957) how ever, d oubted w hether it belongs to this tribe and suggested possible affinities w ith O ryza and Stipa.
D ichelachne.— (T rin. & R upr. 1842; Pilger 1954, 1956). Very little in fo rm a tio n regarding this genus is available. T he aw n, how ever, originates from the back o f th e lem m a as in the Aveneae and Agrosteae a n d , for this reason, the genus should n o t be included in the Stipeae. H u b b ard (1959) a n d G a rd n e r (1952) place Dichelachne in
the Agrosteae.
Aristida and Ampliipogon.— F o r discussion see page 221.
Streptachne.— (H en rard , 1929; K u n th , 1833; T rin. & R upr., 1842; R oshevitz,
1951). T ransferred by H enrard (1929) to Aristida as the section Streptachne w hich accom m odates the single-awned species.
1 . 3 . Ph y l o g e n e t i c Po s it io n
A t the end o f the sub-fam ily Festucoideae, Pilger (1954) lists several tribes, w hich he ap p aren tly regarded as having n o clear affinities. H ere he placed the Stipeae betw een th e Pappophoreae and the Nardeae. Studies o f the a n ato m y a n d em bryo o f the Pappo-phoreae have show n th a t the latter p ro b ab ly is closely related to the Eragrosteae. a n d
can n o t, therefore, be regarded as allied to the Stipeae. It is possible th a t the N ardeae
based largely on leaf an ato m y , B row n (1958, p. 173) placed the Danthonieae and
Stipeae adjacent to each other, a n d indicated th a t the affinities o f these tribes are still u n certain . Stebbins (1956, p. 894), in a d iag ram show ing the evolutionary in te r relationships o f the principal sub-fam ilies a n d tribes, places the Stipeae as an isolated g ro u p a n d regards it as p ro b a b ly a n offshoot o f the Danthonioid-Arundinoid com plex. T he Stipeae differs m ainly from the m em bers o f the D anthonioid-Arundinoid com plex in having strictly one-flowered spikelets, an in d u ra te lem m a tightly enclosing the grain, a terete n o t flattened aw n, a linear hilu m a n d in the internal structure o f the em bryo. T h e Stipeae differs from the Festuceae in th e one-flow ered spikelet, in d u rate lem m a tightly clasping the grain a n d the sm all chrom osom es usually in m ultiples o f 6, 11 o r 12: an d from the Aveneae in th e in d u ra te lem m a tightly clasping the grain, the sm all chrom osom es an d the aw n w hich originates from the apex an d n o t from the back o f th e lem m a.
F ro m the foregoing it is evident th a t until m ore detailed in fo rm atio n concerning the characteristics o f the different tribes is available, the relationship o f the Stipeae
to o th er tribes ca n n o t be determ ined a n d established w ith certainty. As indicated by S tebbins (1956) and by Brown (1958), it will pro b ab ly prove to be an isolated g ro u p w ith no close affinity to any o f the o th er tribes.
In an excellent p ap er on the tertiary p rairie grasses o f the H igh Plains o f N o rth A m erica, Elias (1942, p. 68) traced the relationship o f some o f the “ Stipoid ” genera by m edium o f fossils fou n d in M iocene a n d Pliocene deposits. T he genus Stipa, it is p ostulated, has evolved from tw o different fossil genera nam ely Parastipidium a n d
Stipidium , the form er having given rise to the 6 crow nless sections o f Stipa, w hereas th e latter is considered to be ancestral to the 3 sections possessing crow ns. T h e tribe
Stipeae thus presents one o f the rare cases in the G ram ineae w here the p re-history is know n to som e extent.
1 .4 . Dis t r ib u t io n
T he Stipeae in the concept o f the present a u th o r is restricted m ainly to the tem perate an d wrarm tem perate regions o f b o th hem ispheres, only rarely occurring in the tropics. T he m ajority o f the species, are typical dry grassland in h ab itan ts, how ever, a few are fo u n d in forests o r m oist h ab itats. In the N o rth e rn H em isphere the centres o f greatest co n cen tratio n o f species occur in N o rth A m erica, the M editerranean area, a n d the R ussian Steppes. In the Southern H em isphere the m ost im p o rtan t areas o f d istrib u tio n are S o u th A m erica, A ustralia a n d T asm ania.
A m ong the com ponent genera o f the Stipeae the genus Stipa is the largest a n d also th e m ost widespread. M an y species, p articu larly those o f the S outhern H em isphere, are typical constituents o f desert grassland. T he A ustralian representatives, how ever, fo rm a rath er distinct group, differing in a n u m b er o f m inor characters from the species occurring in other parts o f the world.
O ryzopsis is a small genus confined to the N o rth ern H em isphere. It is closely
related to Stipa.
Nasella, regarded by Parodi as a section o f Stipa, occurs in Peru, Chile an d the A rgentine.
1 .5 . S T IP E A E N ees
A grost. Bras. 371 (1829)
Annual o r perennial herbs, frequently w ith tough, rigid culms. Ligule m em b ran o u s o r m em branous and fim briate, obtuse. Leaf-blade narrow , rolled and wiry, o r fairly wide a n d expanded. Spikelets all sim ilar, bisexual, 1 -flowered, arranged in contracted
o r open panicles. Rhachilla d isarticu latin g above the glum es, n o t p roduced beyond the floret [“ occasionally present as a w art-like pro jectio n at the base o f the p alea ” : Elias (1942)]. Glumes persistent, the u p p er (and often the lower) as long as o r longer th a n the florets. Lem m a usually terete, w ith convolute or involute m argins, rarely hyaline a n d thin, 3-7 (usually 5)-nerved w ith the nerves anastom osing at the apex, aw ned from the entire or m inutely 2-lobed tip ; the aw n apical, single, o r rarely w ith tw o ad d itio n al, shorter, lateral aw ns, three o f the nerves o f the lem m a passing into the aw n ; callus sh o rt o r long, o b tu se o r acute, bearded. Lodicules 3 (rarely 2).
Caryopsis tightly em braced by the lem m a an d p alea; hilum linear, at least h a lf tne length o f the g rain ; em bryo the length o f the grain (Fig. 2, F a n d 4, D). An a t o m y
Leaf-blade expanded, folded or semicircular. Chlorenchyma continuous between the bundles,
n ot arranged in a definite pattern, cells circular or angular. Bundle sheaths two: inner o f small cells with thickened walls; outer or large m ore or less circular thin-walled cells furnished with chloroplasts, gradually merging into the adaxial stereom e or interrupted by the fibres o f the stereome both ad- and abaxially. Epidermis o f a relatively sim ple type: long ripple-walled elements generally rather shallow ly undulate, alternating with paired short elem ents; silicified cells variable, often dum b-bell-shaped (m any species with elongate, square or sub-circular silicified cells), always accompanied by a suberized cell; unicellular hairs o f various types present, two-celled hairs absent; stomata present on the adaxial surface only, or present on both surfaces.
Awn.— Colum n angular to sub-circular in cross-section, occasionally grooved on one side, containing
a large central vascular bundle flanked by 2 groups o f chlorenchym a cells, each subtended by a sm aller, lateral vascular bundle; central bundle surrounded by small or large much-lignified cells; small vascular bundles in close contact with the chlorenchym a on one side, and supported by usually small much-lignified cells on the other; chlorenchym a groups situated just beneath the lateral epidermis; epiderm is opp osite the chlorenchym a groups containing stom ata; seta agreeing anatom ically with the colum n, but the lateral vascular bundles, as well as the layers o f lignified cells surrounding the central bundle disappearing towards the apex, and the groups o f chlorenchym a cells converging and finally contactin g the central bundle.
C aryopsis.— Starch grains com pound; em bryo usually with a well-developed epiblast (occasionally
small but always present); no cleft present between the coleorrhiza and the lower part o f the sc u tellu m : vascular strand diverging into the scutellum directly below the coleoptile; first leaf (sheathed by the coleoptile) with the inflexed margins not overlapping (Fig. 2, E and 4, E, F).
R eferences.— Duval-Jouve, 1875; K ennedy, 1899; H olm , 1901; Hughes, 1921; Prat, 1936; Parodi, 1944; Reeder, 1957.
Ka r y o l o g y
The chrom osom es are small and occur in m ultiples o f 9, 10, 11, 12, 14, 16 and 17. Stebbins ( 1941, p. 379) suggests that m ost o f the numbers found in the aneuploid series o f chrom osom e numbers in
Stipa probably could have been derived from the basic numbers X = 11 and 12. Consequently these
tw o basic numbers probably could also account for the numbers found in the other genera as well, m ost o f them being multiples o f 11 and 12.
Brown & Emery (1957) report for S tipa leucotricha Trin. & Rupr. that in the m itotic division the nucleolus disappears before metaphase. They found the presence or absence o f nucleoli persisting to m etaphase to have som e bearing on classification in the Gramineae, since the nucleolus disappears before metaphase in the subfamily Festucoideae and in a part o f the group Phragm itiform es A vdulov, whereas it persists to metaphase at least in a large percentage o f cases in the subfamily Panicoideae as well as in the O ryzeae, Unioleae and Bambuseae o f the group Phragmitiformes.
G enera; Stipa, Trikeraia, O ryzopsis, Nasella, Piptochaetium.
References.— Avdulov, 1931; H unter, 1934; Stebbins & Love, 1941; Brown, 1951; D arlin gton
1 .6 . De l im it a t io n o f t h e Ge n e r a
Stipa is the largest o f the genera included in the trib e an d also the m ost variable, as testified by the nine sections in to which it is divided by Elias. A lthough Oryzopsis
is retain ed as a distinct genus by practically all a u th o rs, it is closely allied to Stipa
an d som e species are interm ediate betw een these tw o genera [Clem ents ex Elias (1945, p. 71)]. It is fo r this reason th a t, at different tim es a u th o rs have placed one and the sam e tax o n either in Oryzopsis o r in Stipa.
Nasella a genus w ith relatively few species is regarded as distinct by H itchcock
(1950, p. 443) and others, but as a section o f Stipa by Parodi. P arcd i & Freier (1945) studied the genera anatom ically as well as o rg anographically and at present th eir key to the genera appears to be the best available. P aro d i & F reier fo u n d th a t Nasella,
O ryzopsis an d Stipa could n o t be separated solely on anatom ical grounds, w hereas
Piptochaetium is a genus b o th o rg anographically a n d anatom ically distinct.
Trikeraia Bor (1954, p. 555) differs from Stipa in the hyaline, n o t in d u rated lem m a, furnished w ith two sh o rt lateral bristles, form ed by the elongation o f the lateral nerves o f th e lem m a, in addition to the stout m edian aw n typical o f the Stipeae. M o st likely
Trikeraia is correctly placed in the Stipeae. M etcalfe (1960, p. 504) described the
an ato m ical features o f the genus.
T h o u g h it seems fairly certain th a t a greater degree o f uniform ity has been obtain ed by the exclusion o f a n o m alo u s genera from the Stipeae, it is, nevertheless evident th a t in the classification o f the genera retain ed in the tribe progress is im probable unless a m on o g rap h o f the g ro u p as a w hole is u n dertaken. T here are indications th a t an ato m ical studies, particu larly o f the aw n, will be o f considerable value in arriving a t a classification m ore n atu ra l th a n the one existing at present. In fu tu re w ork this aspect should be taken into account.
1 .7 . T H E G E N U S ST IPA
1 .7 .1 . De l im it a t io n
It was decided th a t for the p urpose o f this study it w ould be m ore satisfactory to follow Elias in retaining Stipa as a com prehensive genus subdivided in to sections, th a n to accept the large n u m b er o f ill-defined genera u pheld by Roshevitz an d , to som e extent by Pilger. The S o u th A frican representatives are therefore retained in Stipa
an d provisionally placed in the a p p ro p ria te sections as defined by Elias (1942). It is realized th a t a re-assessm ent o f Elias’ treatm en t o f the sections may necessitate nom en- clatu ral changes, but such a study does n o t fall w ithin the scope o f the present paper.
It m ay be pointed out here th a t R oshevitz (1951), in spite o f dividing the Stipeae
sensu stricto (i.e. w ith the exclusion o f Am phipogon a n d Streptachne) into eleven “ genera ” , did n o t achieve a n a tu ra l g ro u p in g in all respects. F o r instance, he included the A frican Oryzopsis keniensis Pilg., a tax o n indistinguishable from the S outh A frican
Stipa clregeana Steud. var. elongata (N ees) Stapf, in th e genus Piptatherum. U ndoubtedly
this p lan t is m ore closely related to som e A sian an d N o rth A m erican species o f Stipa
placed by Roshevitz in the subtribe Stipiinae, th a n to Piptatherum coerulescens (Desf.) Beauv., the type o f the genus Piptatherum , w hich belongs to the subtribe Timouriinae.
Only tw o sections, Ptilagrostis an d Tort ilia, b o th possessing crow nless lem m as, occur in S o u th Africa. Ptilagrostis consisting o f several species is widely d istributed in N o rth A m erica, E urope and A sia w ith one representative, viz. Stipa dregeana Steud., in A frica. The m onotypic section Tortilia is based on Stipa tortilis Desf. described from N o rth A frica, b u t also occurring in S o u th A frica. F o r reasons o f priority
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1 . 7 . 2 . T h e S o u t h A f r i c a n R e p r e s e n t a t i v e s
Stipa is the only genus o f the Stipeae represented in S o u th A frica. In the m ost recent account o f the South A frican G ram in eae by C hippindall (1955) fo u r species are m entioned. A careful study o f the o rg an o g rap h y an d anatom y o f these species has, how ever, revealed th a t only tw o o f them sho u ld be retained in the tribe Stipeae.
T he use o f the single awn as a generic criterion has proved to be quite u n n atu ral. As early as 1898 S tap f pointed o u t th a t Stipa parvula N ees p robably represented a reduced
A ristida, in w hich the lateral aw ns have disappeared. H en rard (1929), how ever, over
looked this and om itted the species from his m o n o g rap h . Elias (1942) investigated
Stipa parvula organographically a n d con cu rred w ith S ta p f’s view, but did n o t tran sfer th e species to the genus Aristida. C h ip p in d all (1955) an d de W et (1960) likewise rem ark ed on the presence o f m isplaced species o f Aristida in the genus Stipa (on in fo r m atio n supplied by the present au th o r).
In Fig. 1 the fo u r species u n d er consid eratio n are co n trasted : S. parvula an d
S. namaquensis exhibit all the characters regarded as typical o f the Aristideae except
fo r the single aw n, w hereas S. dregeana a n d S. capensis are typical representatives of
the Stipeae. Stipa parvula an d Stipa namaquensis have therefore been transferred to
th e genera Aristida an d Stipagrostis (a section o f Aristida now given generic rank) respectively (pp. 242 and 375). Stipa namaquensis is the sole representative o f a new section viz. Anom ala of the genus Stipagrostis w hereas Stipa parvula is placed in the m o notypic section Schizachne transferred from the genus Stipa to Aristida (p. 236).
1 . 7 . 3 . S T IP A L.
Sp. PI. 78 (1753)
Spikelets solitary, pedicelled, bo rn e in term inal contracted o r open panicles.
R/iachilla disarticulating above the glumes, n o t pro d u ced beyond the base o f the floret.
Floret 1, herm aphrodite, usually sh o rter th a n the glumes, linear in outline. Glumes
persistent, narrow , acute, acum inate o r tip p ed by a bristle (rarely obtuse), 1-3 (rarely 5)- nerved, equal or unequal. L em m a convolute, o r w ith m argins n o t overlapping a t the base, cylindrical or slightly dorsally com pressed, in d u rated a t m aturity, glabrous or hairy, 3-7-(usually 5)-nerved, nerves an asto m o sin g at the apex, apex acute o r m inutely 2 -lobed; awn persistent, single, straight, flexuous o r once to tw ice-geniculate, colum n tw isted, glabrous or hairy, bristle glabrous, p u bescent o r distinctly plu m o se; callus p u n g en t or obtuse, short, o r long bearded. Palea as long as or shorter th a n the lem m a, com pletely enclosed by, o r visible betw een, the m argins o f the lem m a n e a r the base, m em b ran o u s or som ew hat in d u ra ted , 2-nerved. Lodicules 2-3, equal a n d large, or p o sterio r reduced, usually rounded a t the apex, glabrous, indistinctly nerved. Stam ens
2 -3 , a n th ers elongated, som etim es penicillate a t the apex. Ovary g lab ro u s; styles free; stigm as plum ose, apically exserted. Caryopsis tightly enclosed by the lem m a a n d palea, free; hilum linear, slightly sh o rter th a n the grain; em bryo \ (seldom ^) the length o f the grain.
D ensely tufted perennials o r rarely an n u als. Culms usually erect, branched or sim ple; internodes hollow o r solid. Leaf-blades usually long and n arrow , often convolute, m ore rarely flat a n d fairly wide. Ligule m em branous, lacerated, o r a m em b ra n o u s ciliate rim . Panicle n arro w a n d co n tracted , to effuse and open.
A n atom y.— A s described for the tribe.
K aryology.— A s described for the tribe.
Type Species: Stipa pennata L.
213
A very large genus widely d istrib u ted in tem perate a n d w arm -tem perate regions o f the w orld.
1 . 7 . 4 . K ey to the South A frican Species based on O rganographic C haracters Perennial with knotty rhizom atous base; callus o f the floret very short, obtuse; awn 2 -3 times
as long as the lemma, arcuate or once genicu late; palea as long as the lemma, sparsely pube scen t... 1. S. dregeana Annual; callus o f the floret elongated, tapering to an acute point; awn at least eight times as
long as the floret, twice geniculate-, palea much shorter than the lemma, glabrous 2. S. capensis 1 . 7 . 5 . Key Based on A natom ical C haracters
Midrib o f leaf-blade much enlarged and protruding abaxially, furnished with colourless parenchyma surrounding the bundle; first order bundle units wider than deep, hardly protruding adaxially
1. S . dregeana Midrib o f the same size as the other first order bundle units, without additional colourless paren
chym a; first order bundle units broadly ovate in outline and protruding adaxially 2. S. capensis
1 . 7 . 6 . D escription o f the S outh A frican Species
1. S. dregeana Steud., Syn. PI. G lum . 1: 132 (1855). Type: A lbany, H ills near G raham stow n, Drege s.n. ( B t; P R E , fragm ent o f holo.!).
Perennial w ith a short, kn o tty , branched system o f rhizom es. Culms erect, usually sim ple, 3-noded, sm ooth, glabrous, 90-120 cm h ig h ; internodes enclosed in, o r exserted fro m th e sheaths, terete, hollow , glabrous, stria te ; nodes conspicuous, often d a rk in co lo u r, glabrous. L ow er leaf-sheaths reduced to elongated bracts tightly enclosing th e base o f the culm s, increasing in size upw ards, usually sm ooth, striate. Ligule
m e m b ran o u s, up to 5 m m long, obtuse o r lacerated, often w ith the m argins p roduced in to auricle-like outgrow ths. Leaf-blades linear, flat, w idest near the m iddle, up to 12 m m wide a n d 60 cm long, n arro w ed to w ard s the base a n d acum inate, glabrous o r sparsely villous, firm in texture, sm o o th below a n d slightly ro u g h on the nerves ab ove, finely nerved w ith nerves n um erous. Panicle effuse and wide, o r co n tracted an d n arro w , erect or no d d in g , w hen fully developed 15-40 cm long; branches very finely scabrid, single, 2 -3 n ate or fascicled, sh o rt to long an d flexuous, up to 15 cm long, filiform a n d sm ooth. Pedicels scabrid, sh o rter o r longer th an the spikelets. Spikelets
pale green, 6-7 mm long, one-flow ered, linear-lanceolate. Glumes sub-equal, 3-nerved, lanceolate in outline, the low er b ro ad er th a n th e u p p er, finely acum inate, m en b ran o u s an d hyaline in the scabridulous u p p er half. L em m a convolute, n arrow ly lanceolate- cylindric, a b o u t 5-5 m m long, appressed hairy all over, 5-nerved, obscurely bi-lobed w ith a stiff, straight o r a rcu ate aw n from the ap ex ; aw n persistent, scabrid, slightly tw isted below, usually bent a b o u t 2 -4 m m above the base, 10-15 m m lo n g ; callus very sh o rt, obtuse, shortly bearded. Palea subequal to the lem m a, lanceolate, sub- o btuse, n o t keeled, appressed hairy on the back, 2-nerved. Lodicules 3, oblong, obtuse, the tw o a n terio r m em b ran o u s, hyaline, the p o sterio r sm aller. Stam ens 3, an th ers yellow, a b o u t 3 -3 -5 m m long, glabrous. Caryopsis spindle-shaped, brow n, 3 -4 m m lo n g ; hilum linear, black, a b o u t f the length o f the g rain ; em bryo sm all, a b o u t \
the len g th o f the grain, no constriction present beteen the coleorrhiza and the coleoptile (Fig. 2, F.).
Fig. 3.— Distribution o f Stipa dregeana: # v a r . dregeana; O var. elongata; MStipa capensis.
Anatomy (Fig. 2, A, B)
Leaf-blade flat, very thin, wide, tapering gradually towards the margins; abaxial surface flat,
with very few hairs; adaxial surface flat except for the very slightly projecting first order bundle units, with short unicellular hairs flanking the m otor cell groups. A baxial epidermis: S tom atal zones with
215
elem ents; silicified zones: silicified cells dum b-bell-shaped, often with a double constriction and usually accom panied by a short or elongate thin-walled suberized cell with slightly undulate or alm ost sm ooth walls, a few unicellular broad-based retrorse barbs present in this zone, bicellular hairs absent. Vascular
bundle units poorly differentiated, wider than deep, more or less rectangular; first order bundles 9 -13
or m ore, alternating with groups o f 2 -4 second order bundles; bundle sheaths variously interrupted or com plete, outer sheath o f large more or less circular thin-walled cells, inner sheath o f smaller cells o f which the inner tangential walls are strongly thickened. Chlorenchyma cells large, circular or angular, forming a continuous tissue between the bundles; in longitudinal section som ewhat irregular in arrange m ent and with intercellular spaces. Stereom e strands present ad- and abaxially opposite all bundles, strongly developed opposite the first order bundles and less so opposite second order bundles, strands narrow abaxially, wider adaxially especially opposite first order bundles; all strands consisting o f strongly thickened fibres with fairly large cell-lum en. M otor cells fairly well differentiated, all epidermal in origin. M idrib strongly projecting abaxially; midrib bundle surrounded by large thin-walled paren chym a cells (containing no or very few chloroplasts) additional to the parenchymatous outer sheath; inner sheath consisting o f two layers o f cells with strongly thickened walls whereas the other bundles have a single inner sheath. M argin subacute.
Awn: (Fig. 8, A & B). Column roughly triangular in outline with rounded angles, ventral side with
a shallow depression in sections cut near the foot, furnished with three vascular bundles; central bundle large and surrounded by large cells with very strongly asymetrically lignified walls, o f which those situated on the ventral and dorsal sides o f the bundle much exceed the others in size; lateral bundles small and situated near the base o f the central bundle, each subtending a large som ewhat elongated group o f chlorenchyma cells which flank the central bundle and lie directly below the epidermis; epidermis with the outer tangential walls very strongly lignified, furnished with stom ata; seta essentially similar in structure to the colum n but cells surrounding the bundles less lignified and smaller, the lateral bundles disappearing towards the apex o f the seta, the groups o f chlorenchyma cells lying in close contact with the central bundle which in turn is surrounded by relatively thin-walled cells.
C aryopsis: starch grains com pound, consisting o f num erous granules; embryo in sagittal section
show ing the presence o f a well-developed epiblast; the lower part o f the scutellum fused to the coleorrhiza or absent, no cleft being present at the base o f the coleorrhiza; the scutellum bundle diverging directly below the coleoptile (Fig. 2, E); cross-section o f the coleoptile showing the first em bryonic leaf with margins touching but not overlapping, and with three vascular bundles, one median and two lateral, the coleoptile with two lateral bundles and the scutellum with one median bundle. A natom ically no differences could be detected characterizing the varieties.
Ka r y o l o g y
The chrom osom es are o f the small type and 2n = 48 (Fig. 7 N o . 21).
Inflorescences rather dense, usually at least 4 tim es as long as broad, the branches short, densely clustered and bearing spikelets from near the b a se... var. dregeana Inflorescences effuse and open, width about equal to the length, branches long and flexuous bearing
spikelets towards their en d s... var. elongata
{a) var. dregeana.
S. dregeana Steud., Syn. PI. G lum . 1: 132(1855); D ur. & Schinz, C onsp. FI. Afr. 5: 811 (1895); Stapf, FI. C ap. 7: 572 (1898); C hippindall, G rasses and Pastures S.A. 1: 289 (1955).
Lasiagrostis capensis Nees, FI. Afr. A u str., 167 (1841); T rin. & R upr., G ram Stip.. 88 (1842).
Inflorescence dense, m uch elongated.
C a p e .—R iversdale: O akdale, Liebenberg 5617 (a). O u d tsh o o rn : near C ango Caves,
Bolus 12433. U itenhage: R edhouse, Paterson 15946; A ddo, Glennie s.n. P o rt E liza
b eth : K oega, Fairdale 252. A lex an d ria: B oschhoek, A cocks 12089; Sandflats, A rchi bald 5433. C ra d o ck : M o u n tain Z eb ra P ark, Barnard 518; Brynard 30; C rad o ck ,
H olland s.n. A lbany: G rah am sto w n , Godfrey & Story, S.H. 1351; B ritten 2964.
B ath u rst: P o rt A lfred, Tyson s.n. D ep. Agric. N o. 12601; Kowie W est, B ritten 5926; K ow ie, Tyson, Tvl. M us. 17070. K ing W illiam ’s T o w n : K eiskam a Valley, S to ry 3690.
T he d istrib u tio n o f this variety is lim ited to the C ape Province w'here it occurs from the Peninsula to the K ing W illiam ’s T ow n district (Fig. 3). It occurs m ainly in shady places but often in h a b ita ts w hich are m uch m ore arid th an those o f the var.
(b) var. elongata (Nees) S ta p f in FI. C ap. 7: 573 (1898); C h ip p in d all in G rasses a n d Pastures S.A. 1: 289 (1955). T ype: U itenhage, Prim eval forest a t K ra k a k a m m a ,
Drege s.n. (B f; P R E , fragm ent o f holo.!).
Lasiagrostis elongata Nees, FI. A fr. A u str. 168 (1841). L . capensis var. elongata (N ees) T rin . & R u p r., G ram . Stip., 88 (1842).
Stipa elongata (Nees) Steud., Syn. Plant. G lum . 1: 132 (1855).
Oryzopsis keniensis Pilger, N otizbl. Bot. G a rt & M us. Berlin 9: 509 (1926).
Piptatherum keniense (Pilg.) Roshev. in Bot. M a te r H erb ., K am arov, Bot. In st., U .S .S .R . A cad. Sci., 14 (1951).
Inflorescence effuse a n d divaricate, n o t m u ch longer th a n b road.
Ca p e.— C ape Peninsula: C am ps Bay, S trey 772; O range K loof, Adam son 881; K irsten- bosch, Bolus s.n .; Skeleton R avine, M arloth 6048; Bolus s.n. A lex an d ria: O lifants- hoek, Johnson 909. V ictoria E ast: H ogsback, Johnson 1139. C a th c a rt: Liebenberg
5389. Stutterheim : K ologha F o rest, A cocks 9020; D ohne M tn ., Galpin 2455. E ast L o n d o n : near river, Galpin 6533. K ing W illiam ’s T o w n : Sim 20251. K o m g a: G rass valleys n ear K om ga, Flanagan 909; Kei R oad S tatio n , Ranger s.n. K e n ta n i: Chippen-da11 325; A long stream , Pegler 1106. M t. F re re : S to ry 939. U m zim kulu: Insikeni near H o h a, van Tonder 4.
Na t a l.— L io n ’s River: N o ttin g h am R oad, M aclean 955. E stco u rt: Little T ugela R iver, P en tz 178. Bergville: C ath ed ral P eak F o re st Res. S tation, Ind u m en i R iver valley, Killick 1675; The C avern, in fern forest, G em m el 5347. M o n t. aux Sources,
M ogg 5314.
Tr a n s v a a l.— K ru g ersd o rp : M agalies River, Codd 522; W aterval 74, M ogg 23285. S o u tp an sb erg : M alta G orge, Junod 4432; Blaauw'berg, Leipzig M ission, Schw eickerdt
1818.
Br it is h Ea s t Af r i c a: Ke n y a.— N gong, van Som eren A H 9548; M uguga, Verdcourt 1841; N a k u ru , E astern M a u F o re st Reserve, M aas-G e ester anus 6102; L ondiani, T o n d ere t F o rest Reserve, M aas-G eesteranus 4915.
T he variety elongata occurs in the coastal areas o f the C ape fro m the Peninsula to the T ranskei, along the D rak en sb erg escarpm ent in N atal and in a few areas o f the T ransvaal (Fig. 3). It is also fou n d in the cool highlands o f K enya a t altitudes o f over 6,000 feet. Personal observation a n d collectors’ notes indicate th a t it prefers cool, shady a n d m oist conditions. These factors explain, to som e extent, its very in terru p te d d istrib u tio n ; suitable h a b itats being ra re an d occurring a t wide intervals. It is possible th a t it has been over looked in the cool m o u n tain o u s areas o f the R hodesias, U g an d a a n d T an ganyika w here one w o u ld expect it to occur. T he fact th a t it is usually n o t a b u n d a n t in its know n h ab itats is a p o in t in fav o u r o f the la tter view.
Stipa dregeana was described originally by N ees as Lasiagrostis capensis FI. A fr.
A u str., 167 (1841). The genus Lasiagrostis is regarded by m ost au th o rs as synonym ous w ith Stipa, but Roshevitz (1951) retain s it as distinct. If regarded as synonym ous w ith Stipa and retained as a section, the nam e o f the section m ust be Achnatherum
for nom enclatural reasons, as p o in ted o u t by Elias (1942, p. 62) an d H itchcock (1950, p. 216). Investigation, how ever, has show'n th a t S. dregeana does n o t belong to this section sensu stricto, but probably, in agreem ent w ith Elias (1942, p. 64) is provisionally best placed in the section Ptilagrostis. Som e m odification here m ay eventually be desirable since the tw o lobes at the apex o f the lem m a, otherw ise typifying the section, are lacking in S. dregeana. Oryzopsis keniensis Pilger, w hich is conspecific w ith Stipa
dregeana var. elongata, is placed in the genus Piptatherum Beauv. o f the subtribe
Timouriinae Roschev. by R oshevitz (1951). T he type species o f Piptatherum Beauv.
is Piptatherum coerulescens Desf. to w hich S. dregeana is n o t closely related. Pipta
therum coerulescens has a glabrous, ovate lem m a an d an untw isted deciduous aw n,
217
Piptatherum . In S. dregeana the lem m a is cylindric, and in the fruiting spikelet the
palea is slightly exposed tow ards the base of, a n d between the practically parallel m argins o f the lem m a. In m ature specim ens the aw n is often tw isted at the base a n d does not disarticulate. The following species a re ap p aren tly close relatives o f S. dregeana: Stipa
sibirica from E urope, Stipa xaseyii fro m N . A m erica, Achnatherum pekenense (H ance)
Ohwi ( = Stipa extremiorientalis) fro m Ja p a n , a n d Oryzopsis aequiglumis D uthie from the N orth-W est H im alayas. All these species technically belong to the genus O ryzopsis
according to Bor’s delim itation (I960, p. 641) o f Stipa and Oryzopsis. Bor separates
O ryzopsis from Stipa as follow s: “ L em m as elliptic, p lu m p ; aw n eventually deciduous; n o t tw isted b u t curved: callus sh o rt, obtuse, never long an d p o in te d ” . I f B or’s delim itation o f these genera is accepted S. dregeana, alth o u g h possessing a tw isted persistent aw n. could possibly be placed in Oryzopsis. A n o th er fact w hich m ay be o f significance is the shortness o f the epiblast in the em bryo o f S. dregeana (Fig. 2, E). A ccording to R eeder (1957, p. 764) Stipa has a very long epiblast w hich reaches to the tip o f the coleoptile (cf. S. capensis, Fig. 4E) w hereas Oryzopsis has a “ ra th e r sm all epiblast The rath er sh o rt epiblast o f S. dregeana w ould again p o in t to a closer affinity w ith Oryzopsis. The d elim itation o f the genera by different au th o rs, how ever, varies to such a degree th a t at present a tran sfer o f S. dregeana to O ryzopsis seems unjustified.
A new com bination in Stipa based on Lasiagrostis capensis Nees, the oldest nam e for this species, is n o t possible due to the existence o f an earlier hom o n y m . Stipa capensis T h u n b ., an d S. dregeana Steudel therefore is the valid nam e for the taxon w hen placed in the genus Stipa.
2. S. capensis Thunb., P ro d r. 19 (1794); T h u n b ., FI. C ap. ed Schult. 106 (1823); Nees, FI. A fr. A ustr. 1: 170 (1841); T rin. & R u p r., G ram . Stip. 63 (1842); Steud. Syn. PI. G lum . 1: 129 (1855); T ack h o lm & D rar, FI. Egypt, 1: 354 (1941); C h ip p in d all in G rasses & Pastures S. A fr. 1: 290 (1955). T ype: C ape, Thunb. s.n. (U P S , holo.).
S tipa tortilis Desf., FI. A tlant. 1: 99 t. 31, Fig. 1 (1798); K unth, E num . 1 S uppl.: 134 (1835): T rin. & R u p r., G ra m . Stip. 64 (1842); Steud., Syn. PI. G lum . 1: 130 (1855); Boiss, FI. Or. 5: 500 (1884); D u ra n d & Schinz, C onsp. FI. Afr. 5: 812 (1895). S tap f in FI. C ap. 7: 372 (1898).
C aespitose annual. Culms erect o r geniculate, slender, hollow , 10-100 cm high, unbran ch ed or branched from low erm ost nodes, g lab ro u s; internodes usually enclosed by the sheaths, or the upper exserted; nodes glabrous. Leaf-sheaths ra th e r loose, often slipping from the culm s, the up p er w ider an d sheathing the base o f the young panicles, sparsely pubescent to pilose or glabrous. Ligule a m em branous ciliolate rim . Leaf-blades linear, tapering to a fine point, expanded or som ew hat rolled, 5-20 m m long and up to 3 mm wide, glabrous o r sparsely pubescent to pilose below, often scabrid above. Panicle spike-like, narrow , 3-15 cm long; rachis terete, slightly ribbed, scabrous w ith appressed hyaline spines; branches fascicled, scabrous, very unequal, b ranched or simple, up to 7 cm long: pedicels sh o rter th an the spikelets. Spikelets
linear in outline, silvery, 1 -2-1 -6 cm long. Glumes very narrow ly lanceolate to linear, hyaline, silvery, tapering to a fine apex, 3-nerved, the lateral nerves sh o rt; low er usually exceeding the upper in length, u p to 1 -6 cm long; u p p er up to 1-5 cm long. Lem m a
cylindrical, m argins convolute, tightly clasping the grain, indurated, 4 -5 m m long excluding the callus, sparsely bristly, 5-7-nerved, dorsally constricted ju st below the aw n ; aw n solitary, deciduous, articu lated a t apex o f lem m a, 5-8 cm long, colum n twice geniculate, tightly tw isted, h airy ; bristle sh o rt, scabrid; callus pungent, bearded, u p to 2 m m long. Palea m uch sh o rter th a n the lem m a, 1 -25-1-5 m m long, obtuse, som ew hat indurated, 2-nerved. glabrous. Lodicules 2, oblong, m em branous, hyaline, up to 1*5 m m long. Stam ens 3, an th ers yellow, 2 -0 -2 -3 m m long, penicillate. Ovary
glabrous, styles distinct, stigm as plum ose. Caryopsis spindle-shaped, shortly stalked, 3 -3 -5 m m long, brow n; hilum linear, nearly as long as the grain ; em bryo a b o u t
F ig. 4 .— Stipa capensis: A, cross section o f vascular bundles o f the blade; B. diagram o f leaf-blade in cross section; C, abaxial epiderm is o f the leaf-leaf-blade; D , caryopsis show ing the em br>o; E, longitudinal section o f the em bryo; F, cross section o f the em bryo (A cocks
18591).
An a t o m y (Fig. 4, A & B)
Leaf-blade thin and flat, tapering towards the margins, abaxial surface with shallow depressions
between the bundle units which are slightly raised, both surfaces with a few hairs; m idrib only slightly protruding abaxially, not distinctly keeled; margins obtuse to acute. A baxial epiderm is: stoinatal zones with a few stomata or stomata absent and zones consisting o f elongate rectangular ripple-walled
cells usually alternating with short elem ents; short elem ents single or paired, wider than long, occasionally giving rise to short unicellular papilla-like hairs, occasionally much enlarged, and producing very long soft unicellular hairs; bicellular hairs absent; silicified cells small, dumb-bell-shaped.
Vascular bundle units: first order units about 9, trapezoid in outline, alternating with the second order
units; second order bundle units broadly ovate in outline. Bundle sheaths: outer o f large thin-walled parenchym atous cells, in the larger first order bundles supplem ented by large cells both ab- and adaxially and these cells gradually decreasing in size as the walls increase in thickness; thus merging into the fibres o f the stereome; inner sheaths o f m uch smaller cells with the inner tangential walls strongly thickened, the outer walls, however, thin-walled. Chlorenchyma o f irregular thin-walled cells forming a continuou s tissue between the bundles. Stereom e strands com posed o f small fibres, not very strongly developed, present both ab- and adaxially opposite all bundles or occasionally absent adaxially opposite the second order bundles, but always absent opposite the m otor cells. M otor cells rather poorly
differentiated, thin-walled, 5-8 in number, occupying only about ^ the thickness o f the leaf.
Awn: column more or less square in outline, shallow ly grooved ventrally, furnished with three
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the lateral epidermis; epidermis with the outer tangential walls strongly lignified, furnished with stom ata opposite the chlorenchyma groups. Seta similar to the colum n but all cells with thinner walls, towards the apex the lateral bundles disappear and the chlorenchym a cells lie in close contact with the central bundle which is then surrounded by one or two layers o f thin-walled cells.
Caryopsis: starch grains com pound, com posed o f numerous granules; em bryo in sagittal section
show ing the presence o f an extremely elongated epiblast, the lower part o f the scutellum fused to the coleorrhiza, no cleft present at the base o f the coleorrhiza and the scutellum bundle diverging below the coleoptile. The cross-section o f the first em bryonic leaf (sheathed by the coeloptile) with margins touching but not overlapping; the coleoptile with two lateral vascular bundles and the scutellum with one median vascular bundle (Fig. 4 E & F).
C a p e .—G eorge: K aro o in vicinity o f G au ritz River, Ecklon s.n. C la n w illia m :
Schlechter 8588; W elbedacht, M aguire 1855. V anrh y n sd o rp : Ebenezer a t O lifants
River, Drege 8105; Z a n d k raal locally a b u n d a n t in M arginal Strandveld, A cocks 14736; 2 m. N . o f V anrhynsdorp, Schw eickerdt 2558; W iedou River, Barker 9483. C alvinia: G ro o t T oring, A cocks 18591. N a m a q u a la n d : D o o m River Bridge, Taylor 997; W allekraal, between K am ieskroon a n d H ondeklipbaai, Schweickerdt 2565.
I r a q ,— Isbel H am rin near In ja n a , Guest s.n. (N .H . 15797); Isbel D aram ish -k an ,
Guest s.n. (N .H . 16003).
It occurs in the arid p a rts o f the so u th w estern C ape in areas w ith w inter rainfall (Fig. 3), an d is widely d istrib u ted in N o rth A frica a n d the M iddle East. T he in terru p ted d istrib u tio n o f S. capensis follow s a p attern sim ilar to th a t o f m any species in the G ram ineae a n d various o th e r fam ilies (see page 304). This an n u al species is a d ap ted to desert conditions.
G uenzel (1921, p. 6) investigated th e a n ato m y o f the leaf-blade o f S. capensis
(as S. tortilis Desf.) an d his o bservations agree fairly closely w ith the description given above. T he specimen investigated by G uenzel w as collected at E l-K a n ta ra in N o rth A frica.
P A R T 2
T H E T R IB E A R I S T ID E A E
2 .1 . H i s t o r y2 . 1 . 1 . Taxonom ic Studies
F o r a detailed discussion o f the h isto ry o f the nom enclature o f the genus the reader is referred to H e n ra rd ’s in tro d u c tio n to his M o n o g rap h (1929) as well as Schw eickerdt’s in tro d u cto ry rem ark s in his trea tm en t o f the South A frican species (1941).
In the past, Aristida has alm o st invariably been placed in the tribe Stipeae w hich, in tu rn , is treated either as a distinct tribe or as a subtribe or a group o f the Agrosteae.
Since 1875, when D uval-Jouve studied the an ato m y o f the leaf-blade o f two
Aristida species, it has been know'n th a t the a n ato m y o f this genus differs from th a t o f
Stipa, the type genus o f the Stipeae. These an ato m ical differences were, how ever,
n o t regarded to be o f sufficient value to exclude Aristida from the Stipeae. a n d , should there have been no o th er differences between Stipa a n d Aristida, one w ould have been inclined to agree. A vdulov (1931), P ra t (1936) a n d others have, how ever, show n th at the type o f an ato m y o f the leaf-blade is usually closely correlated w ith karyological a n d organographical characteristics. P ro b ab ly influenced by these observations, Roshevitz (1937) transferred the genus Aristida to the tribe Sporoboleae. R oshevitz’s concept o f the Sporoboleae is a wide one a n d includes very heterogeneous elem ents. A natom ically Aristida a n d Sporobolus, how ever, agree fairly closely an d a distan t affinity betw een Aristida, Sporobolus a n d the genera o f the Eragrosteae, w hich have a generally sim ilar anatom y, seems pro b ab le. A discussion o f the relatio n sh ip o f the