XIV 



L YCOPODINEAC 



5°: 



Bower ^ thinks it probable that in S. sphiosa and S. 

 Martensii the sporogenous tissue cannot be traced back 

 always to a single cell (in radial section), and has also shown 

 that when tangential sections are examined, as in Lyco- 

 podium, the archesporium always is a row of cells. 



In all species of Selaginella yet examined, the sporangium 

 is not of foliar origin, but originates from the axis above the 

 insertion of the leaf by which it is subtended. 



As in Lycopodiiivi the tapetal cells do not become dis- 



FiG. 266. — Selaginella Kraussiana (A. Br.). A, Radial section of a nearly ripe microsporangium, 

 X 100 ; /, ligula of the subtending leaf; t, tapetum ; B, section of young macrosporangium (about 

 half grown), showing the papillate tapetal cells (f), x6oo; C, section of the wall of a young 

 macrospore from the same sporangium, x6oo. 



organised, but remain intact as the inner layer of cells of the 

 three-layered sporangium wall. They form an epithelium-like 

 layer of papillate cells, distinguished by their dense granular 

 contents, and it is evident that they are actively concerned in 

 the elaboration of nutriment for the growth of the young spores 

 (Fig. 266). 



As in the other heterosporous Pteridophytes, the two sorts 

 of sporangia are alike in their earlier stages, and this in Sela- 



1 Bower (15), pp. 523, 524. 



