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Gleichenia
Class - Leptosporangiatae
Order- Filicales
Family – Gleicheniaceae
Gleichenia
Gleichenia
 About- 130 sps
 In India- G.linearis, G.glauca
 G.glauca only in Eastern Himalayas
 G.linearis- wide distribution
 Usually in exposed regions, all are
xerophytes and terrestrial
Gleichenia
Sporophyte
 Has long, dichotomously branched,
prostrate , subterranean rhizome
bearing leaves on the upper surface and
adventitious roots on the under side
 Leaves occur in 3 rows though appear to
be in single row
 Leaves- a few feet to 50 mtrs in length
 Leaves show repeated forking-
pseudodichotomy as the rachis growth is
arrested and the pinnae below continue
to grow
 The leaflets lobed, the
incisions reach almost
the midrib so appear as
pinnules
 Has open venation
 Roots- branched-
arranged irregulary/ in
3 rows
Anatomy
 Rhizome-C.S.
 Epidermis- single layer of thin walled
colourless cells
 In some sclerenchymatous and brown
coloured
 No stomata
 Cortex – many layered, broad, may be fully
sclerenchymatous as in G.linearis or outer
sclerenchymatous and inner thin
parenchymatous region as in G.dichotoma
 Stele- protostelic except in G.pectinata
where it is amphiphloic siphonostele in the
internode and solenostele in node.
 In G.linearis and G.dichotoma – it is
mixed protostele
Rhizome-C.S.
Rhizome-C.S.- continued
 Endodermis- single layered- has
casparian bands
 Pericycle – few layered, thin walled ,
surrounds phloem completely
 Xylem occupies the centre- circular in
outline/lobed- usually mixed protostele
 Protoxylem- small patches at the
periphery
Petiole C.S.
 Epidermis- thin walled- single layer
 Cortex- broad- sclerenchymatous
 Endodermis- single layer,
parenchymatous, does not
invaginate the xylem arch
 Pericycle- few layered, completely
surrounds the stele
 Stele- curved C shape with ends
curved inwards
 It surrounds a central
parenchymatous pith
 Protoxylem in small patches in the
concave side of the arch
 Phloem surrounds the xylem
completely
 Pinnule – C.S.
 Has lower and upper epidermis, stomata
only in lower epidermis
 Mesophyll uniform homogenous- has
large air spaces and chlorenchymatous
 Stele- circular in outline
 Vascular bindles collateral
 Phloem faces lower epidermis
 Xylem exarch
Reproduction
 Sori- on the ventral side of the
sporophyll, no indusium, seated on
the lateral veinlet a little behind
the vein endings
 Number of sporangia in a sorus
varies from 4- 15
 Arise on a circular receptacle
 In some sps the centre of sorus is
vacant, in some at the centre
sporangia may be present
 Sporangium- structure- pear shaped,
sessile/ subsessile
 Jacket- single layered
 Oblique annulus may be present
 Next to jacket- 2 layered tapetum
 Tapetal cells disorganize at maturity
to provide nutrition to the young
spores
 At the centre spore mother cells are
present which undergo meiosis to
form haploid spore tetrads
 Number of spore in a sporangium
varies from 128- 1024
 Sporangium splits by a vertical slit
caused by the contraction of annulus
Sporangium- development
 On the ventral side of the
sporophyll, an elevated circular
receptacular surface appears
 Sporangia arise simultaneouly
from the superficial cells of this
region
 Devpt. Is leptosporangiate
 Initials divide by all the three
side
 Cell cut off earlier form the
stalk
 The three segments formed last
form the primary jacket cells
 Finally periclinal division in the
jacket cells form a central
archesporial cell and primary
jacket cell
 Archesporial cell divides by
periclinal and anticlinal
divisions to form two layered
tapetum and innermost primary
sporogenous cell which by
divisions form 32-256 spore
mother cells
 Jacket cells by anticlinal
divisions form complete jacket
around the sporangium
 In the jacket certain cells form the
annulus
 The outer tapetal cells remain small and
flattened but the inner tapetal cells
enlarge and nuclei divide and they
become multinucleate
 Later this layer disorganise and form a
nourishing plasmodial fluid for the
developng spores
Gametophyte
 Spore-small- two types-
1. Trilete spores or tetrahedral
spores (G.glauca, G.linearis etc
2. Monolete spores or bilateral
spore(G.volubilis, G.bifidus etc.)
3. Spore –outer exine /exosporium-
smooth
4. Inner intine- thin
No chloroplast, has scanty
cytoplasm and single nucleus,
food stored as oil drops
 Spore- germination- exine ruptures and
intine comes out as projection
 It divides transversally into ,lower
rhizoidal cell and upper prothallial cell
 Prothallial cell divides by transverse
wall to a form 5/6 celled filament with
chloroplast
 The teminal cell of the filament cut off
an apical cell with two sides which by
further divisions form a elongate
cordate prothallus with distinct midrib
 Prothallus- dorsiventral, green,
cordate with convoluted margins
 Midrib distinct as a narrow groove
on the dorsal side and projects on
the ventral side
 Older prothallus may branch
 Has a thick cushion behind the
apical notch and archegonia
appear on this cushion on the
ventral side
 Protandrous
 Prothallus monoecious
 Antheridia- vary in size in
diff.sps, sessile/subsessile
 Spherical/ globular usually
 Has a single layered thin wall,
distinct triangular opercular cell
 Produces numerous
multiflagellate antherozoids
 Antheridia absorb water, swell
and throw off opercular cell and
the male gametes ooze out
 Archegonia- in the
cushion region behind the
notch on the ventral side
of the proathallus
 Archegonium- has distinct
neck and venter
 Neck- 4 longitudinal rows
of neck cell, 7- 9 cells in
height
 Has as single binucleate neck
canal cell
 Venter- single ventral canal
cell and egg, it is embedded
in the prothallus
 At maturity neck canal cell
and ventral canal cell
disorganise and the neck
opens and a passage for
sperm entry is formed
 Fertilization- sperm enters
through the open passage of the
neck , reaches the egg and fuses
with it to from the dilpoid oospore
is formed which lies in the venter
Embryogeny
 Oospore- first cell of sporophytic
generation
 First division of zygote is vertical-
to form an epibasal cell and
hypobasal cell
 Next division is transverse-
quadrant stage is formed
 Epibasal half – forms stem and
cotyledon
 Hypobasal half- forms the foot and
root
 Foot- conspicuous and haustorial
 Primary root grows into soil and
primary cotyledon pushes upwards
through the notch
 Stem apex grows by a single apical
cell and finally an independent
sporophyte is formed