ch20

Chapter 20

Chapter 20

BRYOPHYTES

BRYOPHYTES

ADAPTATIONS ENABLING THE MOVE TO LAND ADAPTATIONS ENABLING THE MOVE TO LAND

1

1.. A A llaayyeer or off sporopolleninsporopollenin protects charophytes from desiccation; sporopollenin is found  protects charophytes from desiccation; sporopollenin is found in thein the spore wall of land plants.

spore wall of land plants. 2.

2. DangDanger of desiccater of desiccation requion required new adapired new adaptatiotations: transns: transport tissport tissue, cutiue, cuticle, largcle, large compacte compact multicellular ody, etc.

multicellular ody, etc. !.

!. "imu"imultaneltaneous e#oous e#olutilution of cuon of cuticle aticle and stond stomata wimata with guath guard cellrd cells.s. $.

$. "u"upppporort agat againinst gst grara#i#ityty.. %.

%. &epro&eproductduction ecion ecame adaame adapted tpted to perioo periods of mds of moistuoisture so spere so sperms courms could swild swim.m. '.

'. (ame(ametes and spotes and spore mothre mother cells eer cells ecame procame protectetected from dryd from dryness y layness y layers of cellsers of cells.. ).

). *#ol*#olutioution of +ylem and phln of +ylem and phloem to transoem to transport maport materiaterials to and from diffls to and from different paerent parts of the planrts of the plant, thet, the atmosphere and the soil.

atmosphere and the soil. .

. Alternation of generationsAlternation of generations: a characteristic life cycle.: a characteristic life cycle.

•

• Alternation of generation does not occur Alternation of generation does not occur in the charophyceans. -his suggests that alternationin the charophyceans. -his suggests that alternation

of generation arose independently in land

of generation arose independently in land plants. A plants. A life cycle characteried y life cycle characteried y a multicellulara multicellular haploi ga!etoph"te stage

haploi ga!etoph"te stage followed y a multicellular followed y a multicellular iploi sporoph"te stageiploi sporoph"te stage..

•

• M#lti$ell#larM#lti$ell#lar% epenent % epenent e!&r"os'e!&r"os' -he -he ("gote("gote is retained surrounded y tissues of the is retained surrounded y tissues of the

gametophyt

gametophyte. -he e. -he parental tissue pro#ides the emryo parental tissue pro#ides the emryo with nutrients.with nutrients. Pla$ental transferPla$ental transfer $ells

$ells present in the emryo and  present in the emryo and sometimes in the gametophyte as well, enhance the transfer of sometimes in the gametophyte as well, enhance the transfer of  nutrients.

nutrients. /.

/. Spores pro#$e in sporangiaSpores pro#$e in sporangia: haploid reproducti#e cells that : haploid reproducti#e cells that ecome a multicellular haploidecome a multicellular haploid gametophyte y mitosis.

gametophyte y mitosis.

•

• -he multicellular sporangium contains sporocytes, the cells that -he multicellular sporangium contains sporocytes, the cells that undergo meiosis to formundergo meiosis to form

spores. spores. 10.

10. lants are euaryotilants are euaryotic, multicellular, mc, multicellular, mostly autotrophic oostly autotrophic organisms, with haploiddiprganisms, with haploiddiploid lifeloid life cycles, which retain emryo within female se+ organ on parent plant; the

cycles, which retain emryo within female se+ organ on parent plant; the cell wall containscell wall contains cellulose.

cellulose.

)HARA)TERS O* NONVAS)+LAR PLANTS )HARA)TERS O* NONVAS)+LAR PLANTS

Aout 1),000 species worldwide di#ided into three

Aout 1),000 species worldwide di#ided into three Di#isions:Di#isions: Br"oph"taBr"oph"ta, the mosses;, the mosses; Hepatoph"taHepatoph"ta, the, the li#erworts; and

li#erworts; and Antho$eroph"taAntho$eroph"ta, the hornworts., the hornworts. -heir life cycle is similar ut the

-heir life cycle is similar ut the three groups may not e closely related. -he ryophytes may form three groups may not e closely related. -he ryophytes may form aa  polyphy

3ryophyt

3ryophytaa refers to the  refers to the phylum of mosses only; ryophytphylum of mosses only; ryophyt eses refer to the  refer to the three phyla mentioned ao#e.three phyla mentioned ao#e. 4n many respects, ryophytes are transitional etween charophycean green algae and the #ascular plants 4n many respects, ryophytes are transitional etween charophycean green algae and the #ascular plants discussed later in the course.

discussed later in the course. )hara$teristi$s

)hara$teristi$s:: 1.

1. "mall em"mall emryoryophytphytes found in moies found in moist en#irost en#ironmennments, lac wots, lac woody tissody tissue and +ylue and +ylem and phloemem and phloem;; they usually form mats spread o#er the

they usually form mats spread o#er the ground.ground. 2.

2. (ame(ametophytophyte generatte generation is domion is dominantinant; sporop; sporophythyte is parasite is parasitic on the gametic on the gametophyophyte.te. !.

!. 3ryo3ryophyphytes ha#e cutites ha#e cuticle, stomcle, stomata and mulata and multicellticellular gamular gametangetangia and sporaia and sporangia thangia that allow tht allow them toem to sur#i#e on land.

sur#i#e on land. $.

$. -heir o-heir odies are comdies are composed of truposed of true parenche parenchyma deriyma deri#ed from thr#ed from threedimeedimensioensional grownal growth usualth usuallyly from an apical meristem.

from an apical meristem. %.

%. 3ryo3ryophyphytes need water to reptes need water to reproduroduce and most spece and most species laccies lac #ascul #ascular tissuar tissue 5+ylem and phe 5+ylem and phloemloem6.6. '.

'. 7a7ater transpoter transport is rt is mostly tmostly through caphrough capillary actioillary action, diffun, diffusion and sion and cytoplasmic cytoplasmic streaming. streaming. -hey-hey lac true roots, stems and lea#es.

lac true roots, stems and lea#es.

-he gametophyte of mosses is a onecellthic filament nown as the protonema that

-he gametophyte of mosses is a onecellthic filament nown as the protonema that e#entually producese#entually produces  uds ha#ing meris

 uds ha#ing meristematic tissue. -hestematic tissue. -hese meristems produce an upre meristems produce an upright structure called tight structure called thehe ga!etophorega!etophore.. -hese gametophytes are one to a few

-hese gametophytes are one to a few cells thic and otain nutrients and water y direct asorption fromcells thic and otain nutrients and water y direct asorption from the en#ironment.

the en#ironment.

8ost mosses do not ha#e conducting tissue. "ome species ha#e specialied cells that conduct water and 8ost mosses do not ha#e conducting tissue. "ome species ha#e specialied cells that conduct water and nutrients ut lac lignin in their cell walls.

nutrients ut lac lignin in their cell walls. -he gametophores are anchored y fragile

-he gametophores are anchored y fragile rhi(oisrhi(ois. &hioids are either single elongated cells as . &hioids are either single elongated cells as thosethose found in li#erworts and hornworts, or filaments of cells as

found in li#erworts and hornworts, or filaments of cells as those of mosses.those of mosses. &hioids are not made of

&hioids are not made of tissues and do not asor any significant amount of water. 4n that way theytissues and do not asor any significant amount of water. 4n that way they differ from roots.

differ from roots.

3ryophytes ha#e smallest and simplest sporophyte of

3ryophytes ha#e smallest and simplest sporophyte of any group.any group. -he sporophyte remains attached to

-he sporophyte remains attached to the gametophyte throughout its lifetime, dependent of the gametophyte throughout its lifetime, dependent of thethe gametophyt

gametophyte for e for food, water and minerals.food, water and minerals. -he mature sporophyte of mosses consists of a

-he mature sporophyte of mosses consists of a footfoot emedded in the archegonium, a emedded in the archegonium, a setaseta or stal is or stal is  present in the phy

 present in the phylum 3ryophyta, and alum 3ryophyta, and a $aps#le$aps#le or sporangium. -he cap or or sporangium. -he cap or $al"ptra$al"ptra closes the closes the peristo!eperisto!e or opening or the capsule.

or opening or the capsule.

Di,ision Br"oph"ta Di,ision Br"oph"ta

8osses are a

8any new species are disco#ered e#ery year

8any new species are disco#ered e#ery year in the tropics.in the tropics. -he phylum is di#ided into

-he phylum is di#ided into three classes, "phagnosida 5peat mosses6, Andreaeopsida 5granite mosses6 andthree classes, "phagnosida 5peat mosses6, Andreaeopsida 5granite mosses6 and 3ryopsida 5true mosses6.

3ryopsida 5true mosses6.

-he class 3ryidae contains aout

-he class 3ryidae contains aout /,%00 species./,%00 species. )HARA)TERISTI)S

)HARA)TERISTI)S rotonema gi#es rise to

rotonema gi#es rise to gametophores, leafy shoots that produce gametangia.gametophores, leafy shoots that produce gametangia. rotonema chlorophyllous with multicellular

rotonema chlorophyllous with multicellular rhioids.rhioids. (ametophy

(ametophyte may te may or may not ranch.or may not ranch.

(ametophores deri#e from an apical meristem that has a

(ametophores deri#e from an apical meristem that has a large apical cell. Deri#ati#e cells sudi#ide andlarge apical cell. Deri#ati#e cells sudi#ide and  produce the tissues

 produce the tissues of stems and lades in raof stems and lades in rather precise arrangement.ther precise arrangement. (ametophore leafy with more than three rans of

(ametophore leafy with more than three rans of lades.lades. A+is with thic walled outer cortical cells and a central

A+is with thic walled outer cortical cells and a central strand of smaller cells.strand of smaller cells. 9amina sessile, entire, seldom loed, one cell thic.

9amina sessile, entire, seldom loed, one cell thic. 8idri composed of se#eral la

8idri composed of se#eral layers.yers.

9aminar cells elongated; hyaline cells: dead,

9aminar cells elongated; hyaline cells: dead, large, arrelshaped, retain large quantities of water...large, arrelshaped, retain large quantities of water... 4n the family olytrichaceae, the lamina ears long

4n the family olytrichaceae, the lamina ears long sheets of cells 5lamellae6 on the upper surface thatsheets of cells 5lamellae6 on the upper surface that greatly increases the #olume

greatly increases the #olume of photosynthetic tissue.of photosynthetic tissue. Cuticle e+ists only on the upper surface of

Cuticle e+ists only on the upper surface of the lades; the underside lacs cuticle and is capale ofthe lades; the underside lacs cuticle and is capale of asoring water directly from the

asoring water directly from the en#ironment.en#ironment. "tomata are asent on lades ut present on

"tomata are asent on lades ut present on the sporangial wall.the sporangial wall. araphyllia present in some species:

araphyllia present in some species: small, ranched, uniseriate structures.small, ranched, uniseriate structures. -ater transport

-ater transport 1.

1. 4n some mos4n some mosses, primses, primarily in the famarily in the family olyily olytrichatrichaceae, the inceae, the innermonermost corte+ is comst corte+ is composed of celposed of cellsls called

called h"roish"rois that conduct water and dissol#ed minerals. that conduct water and dissol#ed minerals.

•

• *longated cells that loose their c*longated cells that loose their cytoplasm at maturityytoplasm at maturity.. •

• *nd walls are *nd walls are partially digested ut are not partially digested ut are not remo#ed completelyremo#ed completely.. •

• *ach hydroids are aligned with those ao#e and elow it*ach hydroids are aligned with those ao#e and elow it

2.

2. "pe"peciecies thas that ha#t ha#e hyde hydroiroids tyds typicpicallally ha#y ha#ee leptoisleptois. 9eptoids resemle sie#e cells.. 9eptoids resemle sie#e cells.

•

•

• 9ac nuclei at maturity ut retain some c9ac nuclei at maturity ut retain some c ytoplasmytoplasm.. •

• a#e prominent interconnections with adacent cells.a#e prominent interconnections with adacent cells.

!.

!. AdacAdacent pareent parenchynchyma cells are unusma cells are unusually cyually cytoplastoplasmic and rich in enymic and rich in enymes ust as are compmes ust as are companionanion cells.

cells. -he maority of

-he maority of mosses lac hydroids and leptoids. 7atmosses lac hydroids and leptoids. 7ater is er is conducted long the e+terior of conducted long the e+terior of their stems ytheir stems y capillary action.

capillary action.

4n species that lac leptoids, sugar is transported y slow transport etween the cells. 4n species that lac leptoids, sugar is transported y slow transport etween the cells. At the ase of the a+is,

At the ase of the a+is, rhi(oisrhi(ois anchor the plant ut do  anchor the plant ut do not asor water or nutrients.not asor water or nutrients.

•

• 8ulticellular filaments8ulticellular filaments •

• -hey lac chloroplasts-hey lac chloroplasts

De,elop!ent De,elop!ent

"pores germinate and send out a

"pores germinate and send out a long chlorophylong chlorophyllous cells.llous cells.

-his cells undergoes mitosis and produces a ranched system of similar cells called the

-his cells undergoes mitosis and produces a ranched system of similar cells called the protone!aprotone!a..  <odules of small cy

 <odules of small cytoplasmic cells form on the protoplasmic cells form on the protonema, organie an apitonema, organie an apical cell, and then grow upcal cell, and then grow uprightright as a stem with lea#es,

as a stem with lea#es, thethe ga!etophorega!etophore..

rotonemata are perennial and can produce many uds. rotonemata are perennial and can produce many uds.

Repro#$tion Repro#$tion

All mosses are oogamous; that is they produce a

All mosses are oogamous; that is they produce a small flagellated sperm and a large nonmotile egg.small flagellated sperm and a large nonmotile egg. 8ale and female gametangia, called

8ale and female gametangia, called antheriiaantheriia and and ar$hegoniaar$hegonia respecti#ely, co#ered with a protecti#e respecti#ely, co#ered with a protecti#e layer of cells, a

layer of cells, a sterile acet layer.sterile acet layer.

&etention of the ygote and de#eloping multicellular emryo within the archegonium of the female &etention of the ygote and de#eloping multicellular emryo within the archegonium of the female gametophyte.

gametophyte.

"pecies may e ise+ual 5antheridia and archegonia on the same

"pecies may e ise+ual 5antheridia and archegonia on the same gametophore6 or unise+ual 5antheridiagametophore6 or unise+ual 5antheridia and archegonia on separate

and archegonia on separate gametophore6.gametophore6. Archegonia apical 5acrocarpous6 or on

Archegonia apical 5acrocarpous6 or on reduced ranches 5pleurocarpous6.reduced ranches 5pleurocarpous6. Sporoph"te generation

Sporoph"te generation 4n all emryophytes, the

4n all emryophytes, the megagamete and susequentlymegagamete and susequently, the , the ygote, are retained y ygote, are retained y the gametophyte.the gametophyte. 8oss gametophytes are large and

3ryophytes ha#e smallest and simplest sporophyte of

3ryophytes ha#e smallest and simplest sporophyte of any group.any group. -he sporophyte remains attached to

-he sporophyte remains attached to the gametophyte throughout its lifetime, dependent of the gametophyte throughout its lifetime, dependent of thethe gametophyt

gametophyte for e for food, water and minerals.food, water and minerals. -he mature sporophyte of mosses consists of a

-he mature sporophyte of mosses consists of a footfoot emedded in the archegonium; a emedded in the archegonium; a setaseta or stal is or stal is  present in the Di#i

 present in the Di#ision 3ryophysion 3ryophyta, and ata, and a $aps#le$aps#le or sporangium. -he ape+ of the  or sporangium. -he ape+ of the sporangiumsporangium differentiates into a lidlie

differentiates into a lidlie oper$#l#!oper$#l#!. -he operculum separates from the rest of . -he operculum separates from the rest of the sporangium as cellsthe sporangium as cells differentiate into teeth called peristome teeth. -he

differentiate into teeth called peristome teeth. -he $al"ptra$al"ptra closes the closes the peristo!eperisto!e or opening or the or opening or the capsule. -he calyptra is deri#ed from the nec of

capsule. -he calyptra is deri#ed from the nec of the archegonium.the archegonium.

"porangium opens y an apical lid eneath which the peristome teeth are

"porangium opens y an apical lid eneath which the peristome teeth are present.present. -he peristome teeth end outward and open the sporangium when the air

-he peristome teeth end outward and open the sporangium when the air is dry allowing the spores tois dry allowing the spores to escape when they are not sticy and

escape when they are not sticy and can e easily dispersed y air currents. -he teeth can e easily dispersed y air currents. -he teeth end inward whenend inward when the air is humid.

the air is humid.

Columella in the sporangium. Columella in the sporangium.

"eta long and wiry; sporophyte persists for a long period. "eta long and wiry; sporophyte persists for a long period. "eta elongates efore sporangium is

"eta elongates efore sporangium is fully differentiated.fully differentiated. 8ost mosses are

8ost mosses are homosporous.homosporous. A few species produce two ind

A few species produce two ind of spores: large spores that of spores: large spores that produce gametophytes with archegonia, andproduce gametophytes with archegonia, and small spores that produce gametophores with

small spores that produce gametophores with antheridia.antheridia. Meta&olis! an E$olog"

Meta&olis! an E$olog"

9ea#es of moss gametophores are thin with a

9ea#es of moss gametophores are thin with a cuticle only on the upper surface. 8osses dry cuticle only on the upper surface. 8osses dry out in a fewout in a few minutes.

minutes.

"e#eral mechanism compensate for the inaility of mosses to retain water. "e#eral mechanism compensate for the inaility of mosses to retain water.

•

• 8any moss species li#e in permanent moist en#ironment: cloud forest, near waterfalls, spray8any moss species li#e in permanent moist en#ironment: cloud forest, near waterfalls, spray

ones, etc. ones, etc.

•

• 8icrohaitats, e.g. foot of rocs, shallow depressions of sustrate, etc.8icrohaitats, e.g. foot of rocs, shallow depressions of sustrate, etc.

"ome species are tolerant of desiccation. -hey must maintain at least !0=

"ome species are tolerant of desiccation. -hey must maintain at least !0= of their ody weight water.of their ody weight water. 7ater is asored rapidly if it rains or dew forms.

7ater is asored rapidly if it rains or dew forms.

8osses remain acti#e during certain seasons of the year

8osses remain acti#e during certain seasons of the year depending on the ecosystem in which they li#e:depending on the ecosystem in which they li#e:

•

• 4nacti#e during dry spells during the summer in mild temperate regions.4nacti#e during dry spells during the summer in mild temperate regions. •

• -urg-urgid during winter months in id during winter months in deserts and dry deserts and dry haitats.haitats. •

• Acti#ity also #aries during the Acti#ity also #aries during the day.day.

8osses are #ery resistant to high and low

8any moss species remain acti#e during winter months when there is enough

8any moss species remain acti#e during winter months when there is enough moisture e#en if themoisture e#en if the temperature is elow 0@C.

temperature is elow 0@C.

8oss together with lichen species are the primary coloniers of ear

8oss together with lichen species are the primary coloniers of ear rocs, stone walls and tree truns.rocs, stone walls and tree truns. 8osses help to control runoff during rains y asoring water and holding it lie a

8osses help to control runoff during rains y asoring water and holding it lie a sponge and thensponge and then releasing it slowly.

releasing it slowly.

DIVISION HEPATOPHYTA DIVISION HEPATOPHYTA

-here are aout ',000 species of li#erworts or hepatics. -here are aout ',000 species of li#erworts or hepatics. 8ost li#erwort gametophytes de#elop directly from spores

8ost li#erwort gametophytes de#elop directly from spores ut some produce protonemata.ut some produce protonemata. -he gametophyte may e leafy or

-he gametophyte may e leafy or thalloid.thalloid.

-he plant typically is flattened with distinct dorsal and #entral surfaces 5

-he plant typically is flattened with distinct dorsal and #entral surfaces 5 orsi,entralorsi,entral6.6. )HARA)TERISTI)S

)HARA)TERISTI)S

(A8*-B-* (*<*&A-4< (A8*-B-* (*<*&A-4<

-he gametophyte phase egins with the germination of spores. rotonemata are formed. -he gametophyte phase egins with the germination of spores. rotonemata are formed. -he protonemata are ne#er long li#ed or

-he protonemata are ne#er long li#ed or highly ramified lie in mosses. After a few cells are produced,highly ramified lie in mosses. After a few cells are produced, and apical cell is formed and

and apical cell is formed and the growth of the gametophyte egins.the growth of the gametophyte egins. Leaf" li,er.orts

Leaf" li,er.orts

-here are aout $000 species of leafy

-here are aout $000 species of leafy li#erworts.li#erworts. -hey are aundant in areas of

-hey are aundant in areas of high humidity and rainfall of the tropics and sutropics.high humidity and rainfall of the tropics and sutropics. -he leafy growth hait consists of three rows of

-he leafy growth hait consists of three rows of isomorphic lea#es or in dorsi#entral forms two rows ofisomorphic lea#es or in dorsi#entral forms two rows of lateral lea#es with or without a reduced row of

lateral lea#es with or without a reduced row of #entral underlea#es. -he plant resemles a moss.#entral underlea#es. -he plant resemles a moss. 9ea#es generally consist of a single layer of undifferentiated cells, and lac a

9ea#es generally consist of a single layer of undifferentiated cells, and lac a midri. -he ape+ ismidri. -he ape+ is rounded while the ape+ of moss lades are

rounded while the ape+ of moss lades are pointed.pointed. il glands are present in the gametophyte.

il glands are present in the gametophyte.

Antheridia are produced on short side ranches with modified lea#es called the

Antheridia are produced on short side ranches with modified lea#es called the anroe$i#!anroe$i#!.. A tuular sheath called the perianth surrounds the

A tuular sheath called the perianth surrounds the archegonium.archegonium. Thalloi li,er.orts

Thalloi li,er.orts

-he thalloid li#erworts may e comple+ or simple. -he thalloid li#erworts may e comple+ or simple.

-he gametophyte is rionlie or heart shaped, ilaterally symmetrical. -heir ody is called a

(rowth occurs such that the li#erwort creeps along a #ertical or

(rowth occurs such that the li#erwort creeps along a #ertical or horiontal sustrate.horiontal sustrate. 3ranching is dichotomous.

3ranching is dichotomous. (ametophy

(ametophytes grow through the tes grow through the acti#ity of a single apical cell.acti#ity of a single apical cell.

Comple+ thalloid li#erworts e+hiit differentiation of the thallus into strata: Comple+ thalloid li#erworts e+hiit differentiation of the thallus into strata:

•

• An upper photos"ntheti$ regionAn upperphotos"ntheti$ region including air chamers or pores. including air chamers or pores. •

• A #entrally storage (oneA #entrallystorage (one which contains cells with aundant lipid reser#e. which contains cells with aundant lipid reser#e.

-he lower surface ears rhioids. -he lower surface ears rhioids.

"imple thalloid li#erworts lac specialied air chamers ut may contain undles of water conducting "imple thalloid li#erworts lac specialied air chamers ut may contain undles of water conducting tissue.

tissue. -he simple

-he simple thalloid li#erwortsthalloid li#erworts  Riccia Riccia and and Ricciocarpus Ricciocarpus grow in damp soil or are aquatic. grow in damp soil or are aquatic. &iccia may e unise+ual or ise+ual; &icciocarpus is ise+ual.

&iccia may e unise+ual or ise+ual; &icciocarpus is ise+ual. &eproducti#e organs are distriuted along the dorsal

&eproducti#e organs are distriuted along the dorsal surface of the surface of the gametophygametophyte.te. -he sporophyte is deeply emedded in the gametophyte and consists mostly of a

-he sporophyte is deeply emedded in the gametophyte and consists mostly of a sporangiumsporangium..  Marcha

 Marchantiantia produces the se+ organs in specialied structures called produces the se+ organs in specialied structures called ga!etophoresga!etophores 5or 5or gametangiophores6.

gametangiophores6.

•

• Antheriiophores ear antheridia.Antheriiophores ear antheridia. •

• Ar$hegoniophores ear archegonia.Ar$hegoniophores ear archegonia.

(A8*-B-* (*<*&A-4< (A8*-B-* (*<*&A-4< -he sporophyte consists of a short

-he sporophyte consists of a short footfoot,, setaseta and the and the sporangi#!sporangi#! co#ered y a  co#ered y a calyptra.calyptra. -he sporangium lacs columella.

-he sporangium lacs columella. -he sporangium contains spores and

-he sporangium contains spores and elaterselaters to help in  to help in scattering the spores.scattering the spores. Eragmentation and

Eragmentation and ge!!a $#psge!!a $#ps are methods of  are methods of ase+ual reproduction.ase+ual reproduction.

&iccia and &icciocarpus ha#e a simplified sporophyte. -he ygote grows into a spherical mass within the &iccia and &icciocarpus ha#e a simplified sporophyte. -he ygote grows into a spherical mass within the archegonium of the gametophore ody

archegonium of the gametophore ody. <o foot or . <o foot or seta is formed. -he inner cells undergo meiosis andseta is formed. -he inner cells undergo meiosis and form spores. -he spores are lierated when the surrounding tissue dies.

form spores. -he spores are lierated when the surrounding tissue dies.

DIVISION

DIVISION ANTHO)EROPHYTANTHO)EROPHYTAA

ornworts form a small phylum of aout 100 species. ornworts form a small phylum of aout 100 species.

-he gametophyte of hornworts resemles that

-he gametophyte of hornworts resemles that of li#erworts.of li#erworts.

9i#erworts and hornworts are distantly related as shown y eing included in separate phyla. 9i#erworts and hornworts are distantly related as shown y eing included in separate phyla. -hey grow hidden among #egetation and seldom grow on rocs or

-hey grow hidden among #egetation and seldom grow on rocs or tree truns.tree truns. (A8*-B-* (*<*&A-4<

(A8*-B-* (*<*&A-4<

-he germinating spore produces three or four protonema cells efore the thallus egins to

-he germinating spore produces three or four protonema cells efore the thallus egins to de#elop.de#elop. (ametophy

(ametophytic tic thallus loed, sometimes thallus loed, sometimes ranching dichotomouslyranching dichotomously.. -he thallus ecomes round when

-he thallus ecomes round when growing in isolation.growing in isolation. 8ost species ha#e a

8ost species ha#e a single $hloroplastsingle $hloroplast with with p"renoip"renoi in each cell.  in each cell. -his single chloroplast is found in-his single chloroplast is found in algae ut not in other land plants.

algae ut not in other land plants.

"ome species ha#e many small chloroplasts and no pyrenoids ut the apical cell

"ome species ha#e many small chloroplasts and no pyrenoids ut the apical cell contains only onecontains only one reflecting the ancestral

reflecting the ancestral condition.condition. -he upper surface of the thallus is

-he upper surface of the thallus is smooth in some species and other species ear lamellae.smooth in some species and other species ear lamellae. -he thallus is three or four cell

-he thallus is three or four cell thic in the center and thin on thic in the center and thin on the edges. 4t is parenchymatous.the edges. 4t is parenchymatous. -hey do not tolerate drying. 4n temperate ones

-hey do not tolerate drying. 4n temperate ones they appear in the autumn, grow during the they appear in the autumn, grow during the winter andwinter and  produce sporophy

 produce sporophytes in the spring, dytes in the spring, dying efore the summer sets in.ing efore the summer sets in. -he thallus has

-he thallus has internal $ha!&ersinternal $ha!&ers inhaited y the  inhaited y the cyanoacteriacyanoacteria  Nostoc Nostoc..

•

•   Nostoc  Nostoc is nitrogenfi+ing acteria that supply it to the hornwort. is nitrogenfi+ing acteria that supply it to the hornwort.

"ome species ha#e pores that resemle stomata. "ome species ha#e pores that resemle stomata. &hioids are

&hioids are unicellularunicellular.. 8ost species are ise+ual. 8ost species are ise+ual.

Antheridia and archegonia are emedded in the upper surface of

Antheridia and archegonia are emedded in the upper surface of the thallus.the thallus. (ametangia de#elop from superficial cells ut ne#er proect ao#e the surface. (ametangia de#elop from superficial cells ut ne#er proect ao#e the surface. 8ultiple fertiliations occur and many sporophytes may

8ultiple fertiliations occur and many sporophytes may de#elop on the gade#elop on the ga metophymetophyte.te.

"&B-* (*<*&A-4< "&B-* (*<*&A-4<

"porophytes are of indeterminate growth. "porophytes are of indeterminate growth. "porophyte consists of a

"porophyte consists of a footfoot emedded in the gametophyte and a emedded in the gametophyte and a long $aps#lelong $aps#le or  or sporangium.sporangium. A meristem

-his intercalary meristem remains acti#e as long as the

-his intercalary meristem remains acti#e as long as the conditions for growth remain fa#orale.conditions for growth remain fa#orale. -he sporophyte resemles a long

-he sporophyte resemles a long hornlie cylinder.hornlie cylinder. -he sporophyte is green ha#ing

-he sporophyte is green ha#ing se#eral layers of se#eral layers of photosynphotosynthetic cells.thetic cells. -he sporophyte has stomata present.

-he sporophyte has stomata present.

Dehiscence occurs along two longitudinal lines eginning at the Dehiscence occurs along two longitudinal lines eginning at the ape+.ape+. "pores and

"pores and elaterselaters de#elop inside the  de#elop inside the sporangiumsporangium.. A columella is present in the