GROUP III. PTERIDOPHYTA : LYCOPODIN^. 



429 



Rhizophore and root are both monostelic, and without air-chambers : the 

 stele is monarch. 



The bundles are all closed ; there is no secondary growth in thickness. 



The leaves are very simple in structure : they have a midrib with a single 

 /ascular bundle : the epidermal cells contain chloroplastids which, like those in 

 the other cells, are large and are present in small numbers (sometimes only one) 

 in the cells. The stomata are usually confined to the under surface, on the 

 sides of the midrib. 



The growth in length of the stem is effected by an apical growing-point which 

 has, in some species (e.y. S. Martensii) a two-sided or three-sided apical cell, 

 whilst in others (e.g: S. Lyalli, Pervillei, etc.) it consists of small-celled stratified 

 meristern. The structure of the growing-point of the rhizophore agrees with 



B 



FIG. 279. Embryogeny of Selaginella Martensii (after Pfeffer). Two isolated embryos at 

 different stages. A Younger embryo ( x 610) B older ( x 165) : 8 susnensor; c l c 3 cotyledons; 

 ststem; i young foliage-leaves; hyp hypocotyl ; r root ; /so-called foot. 



that of the stem in the various species : but the apical cell, when present, is a 

 four-sided pyramid at first, becoming eventually two-sided. The growing- 

 point of the root has a tetrahedral apical cell. 



Embryogeny of the Sporophyte. The embryogeny of Selaginella closely re- 

 sembles that of Lycopodium. The oospore undergoes division, a transverse 

 basal wall being formed: the upper or hypobasal cell developes into a uni- 

 cellular or few-celled suspensor which is homologous with the foot iu the 

 Bryophyta : the lower or epibasal cell appears to undergo division into four 



