STRUCTURE OF SELAGINELLA 317 



which is bridged either by strands of cortical cells, or by radially 

 elongated endodermal cells. The roots and rhizophores are 

 peculiar in exhibiting but a single protoxylem group. 



The cones, again situated at the ends of usually erect branches 

 (Fig. 180, C), exhibit four rows of sporophylls, all of the same 



FIG. 1 80. A and B, Selaginella martensii (original). A, Part of a plant 

 showing the leafy shoots, the rhizophores (rh.), and the roots arising 

 from their ends. B, Small part of a branch enlarged, to show the two 

 kinds of leaves. C, Plant of 5. spinosa (after Wettstein), showing two 

 cones. D, Sporophyll, and E, foliage leaf of S. spinosa (after Hie- 

 ronymus). Sp., sporangium. 



size and shape, and each with an axillary sporangium borne on a 

 short stalk (Fig. 180, D, Sp. ; Fig. 181, A, E). The sporangia 

 are of two kinds : the one kind (microsporangia) , generally found 

 towards the apex of the cone, are filled with numerous small 

 microspores (Fig. 181, A, mi.) ; the other kind (megasporangia) 

 each contain only four large megaspores (Fig. 181, A, mg.). 



