SPORE-PRODUCING MEMBERS 417 



abaxial loculus which will be thus traversed. A truly radial section of a 

 young synangium is shown in Fig. 232 B, the arrow indicating the direc- 

 tion of the main axis : the cell ( x ) is a conical cell, which is commonly 

 though perhaps not constantly found occupying the centre of the apical 

 surface of the synangium. The cell shaded is believed to be the arche- 

 sporial cell for one of the loculi, but after comparison of a large number 



.-/ B C 



A 



.' , L - 



Psiloiitni triquetrum, Sw. Various stages of development of the synangium and 

 sporangium. In C the sporogenous group is shaded. D shows the differentiation of its 

 cells, the fertile cells being shaded. shows the disorganisation of the remaining cells 

 without forming spores, x 100. 



of sections I am still uncertain whether the whole of the sporogenous tissue 

 in each loculus is really referable to a single parent cell, for just the same 

 difficulty arises here as in Tmesipteris in recognising the exact limits of 

 the sporogenous masses. 



The subsequent stages of development are illustrated by Figs. 232 c, D, E, 

 and it will be seen from these how the sporogenous masses assume large 

 dimensions, and are at first composed of uniform cells. The wall of the 

 synangium meanwhile becomes naultiseriate, and the cells of the outermost 

 layer assume a deep and prismatic form, while the inner layers are narrow. 



2D 



