PTERIDOPHYTE , SELAGINELLA

Introduction
Internal morphology of plant shows the structure and arrangement of cells in the plant body. In this section we are going to have a look to internal morphology of selaginella stem,leaf,root & ligule
                                                                          
       Selaginella sporophytic plant body
 
STEM
* Cutinised
* Divided in to 3 regions. Epidermis, cortex, vascular cylinder or stele
* Epidermis - uniseriate - prosenchymatous (  plant tissue consisting of long narrow cells with pointed ends)
* Devoid of stomata and hairs
* Cortex :- multiseriate - compactly arranged parenchyma cells
* In maturity cortex is differentiated into two
* Outer cortex - thick walled lignified parandhama - hypodermis
* inner cortex - thin- walled - chlorenchyma
* In xerophytes cortex - only thick-walled schlerenchyma
* Endodermis :- radially elongated endodermal cells -trabeculae
* They posses casparian  bands on lateral sides
* Stele :- stele is separated by large air sacs from trabeculae
* Core is protostele - xylem surrounded by phloem

Stelar organisation of stem varies considerably with different species of selaginella. Number of stekes may vary 1,2 very rarely more. It is covered by a single layered pericycle. Shape of stele varies circular, ribbon-like,flat etc..
                T.S of Selaginella stem
LEAF
* Differentiated in to 3 regions Epidermis, mesophyll and stele
* Epidermis : both upper and lower epidermis uniseriate
* They have chloroplast 
* Most cases amphystomatic ( both sides have stomata
* And in sone case hypostomatic ( stomata restricted to outer side)
* Mesophyll :- loosely arranged - thin- walled cells - spongy parenchyma ( in dome case palisade tissues are also present towards the upper side 
* Mesophyll chloroplast posses- spindle shaped & perinoid- like bodies
* Vascular region :- central xylem surrounded by phloem ( protostele)
With bundle sheath
                 T.S of Selaginella leaf
ROOT
* Differentiated in to 3 regions Epidermis, cortex & vascular region
* Epidermis : Tangenty elongated cells. Root hair's are present
* Cortex : Homogeneous - thin- walled cells . But in some species it has differentiated to outer cortex has thick - walled it forms hypodermis and inner cortex region forms endodermis
* Vascular region : 2-3 layers of parenchymatous pericycle- protostele - xylem surrounded by phloem
              T.S of Selaginella root
Rhizophore
* Cutinised
* Differentiated in to epidermis, cortex & vascular region
* Epidermis : single layer- no root hair's are present
* Cortex : outer cortex - schlerenchyma - hypodermis
* Inner cortex - large parenchymatous cortex  - innermost layer act as - endodermis
* Vascular region : parenchymatous pericycle- protostele - xylem surrounded by phloem
      T.S of Selaginella rhizophore
LIGULE
* Pointed outgrowth - base of leaf
* Differentiated in to 3 regions glossdopodium,body & terminal lamella
* Glossdopodium : enlarged- hemispherical base portion - large thin - Walled polygonal cells - rich in granular cytoplasm- surrounded by glossdopodial sheath - tubular cells ( Casparian strips)
* Body : cylindrical middle portion- isodiametric cells- density packed
* Terminal lamella : pointed tip- isodiametric cells- density packed
                T.S of Selaginella ligule

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