PTERIDOPHYTE , SELAGINELLA

Introduction
External Morphology
A pteridophyte is a vascular plant that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden.
                                                                        
One of the plant belongs to the group pteridophyte is Selaginella  
                  Habit of Selaginella
* Commonly called as spike moss or small clubmoss  
* Show Cosmopolitan distribution
* Almost 700 species Verity
* Shows wide range of habit. Shaded moisture tropical forests, extremely dry conditions, on tree trunk etc...
* They act as free living, epiphyte, xerophytes etc..
* Used as ornamental plant 

SPOROPHYTE
Plant body is sporophyte. Shows considerable variations according to varying species. Sporophytic plant body is broadly classified into 2 sub-genera 
(i) Homoeophyllum
(ii) Heterophyllum

HOMOEOPHYLLUM
* Erect , dichotomously branched stem
* leaves are isophyllous ( same type)
HETEROPHYLLUM
* Prostrate, dorsiventral stem with erect branches. Foliage leaves are arranged in 4 rows. 2 row leaves are small and another 2 row are large.
         Four rows of leaf arrangement
Sporophytic plant body is differentiated in to 
Root 
Stem
Leaves
Rhizophore ( sometimes)
                                                                        
STEM
Erect in Homoeophyllum & prostrate dorsiventral in Heterophyllum. Branching of stem is always dichotomous. Reproductive structures are called strobili like or spikes. 
                        stobili on stem 
* Apical growth is directed by single apical cell or by group of apical initials..
LEAVES
* Stem is covered by 4 rows of leaves
* Two of them are small & another onece are large
* They are simply, sessile in most case ovate in shape
* In xerophytes, thick & rigid leaves are present
* In normal plants leaves are delicate and thin
* Tounge- like small structures are present in the bottom of leaves , known as ligule.
* Basal part of ligule has foot-like structure called glossdopodium
* Leaves has a unbranded midrib
* In Homoeophyllum leaves are monomorphic ( same )
* In Heterophyllum leaves are dimorphic
                                                                        
ROOT
* Roots are arise from stem dichotomy
* Some of them arises from knot-like structures called rhizophore
             diagrammatic representation of Selaginella
                                                                     
RHIZOPHORE
* Long , cylindrical, unbranded
* Colourless & leafless
AS ROOTS
* It is positively geotropic
*  it does not bear roots
* Anatomy is similar to that of roots
* Root cap is present at the tip

AS STEM 
* Root hair's are absent as stem
* Rhizophore are arise exogenously( roots arise endogenously)
* They grow by means of single meristem as shoot 
                                                                          

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