THE HOMOSPOROUS LEPTOSPORANGIATJE 



365 



The Sporangium 



The sporangia in Osmund a are produced upon sporophylls 

 that closely resemble those of Bofrycliinm or H elminthostachys , 

 but in Todca they occur upon the backs of the leaves, as in 

 most Ferns. In structure and development they are intermedi- 

 ate between the true leptosporangiate type and the eusporangi- 

 ate. So far as they have been investigated they all correspond 

 very closely. The origin of the sporangia is almost identical 

 witli that in Botrychhim, and more than one cell may take part 



A. 



Fig. 207. — A, Pinnule of a fertile leaf of Todea (Leptopteris) hymenophylloides, X2; 

 B, fertile pinnule of Osmunda Claytoniana, X3; C-E, three views of the ripe 

 sporangium of O. cinnarnomea, X40; F, G, sporangia of Todea Iiymenopliylloidcs, 

 X40; r, annulus. 



in their formation (Bower (ii); Goebel (17)). Bower 

 says: "In all cases, however, one cell distinctly takes the lead, 

 and this we may call the initial cell (Fig. 206, A) ; but the 

 arrangement of its division wall does not, as in the true lepto- 

 sporangiate Ferns, conform to any strict plan ; the initial cells 

 are oblong, seen in vertical section, and the first divisions are 

 longitudinal, so as to meet the basal wall : both in the segment 

 thus cut off and in the central cell, periclinal or sometimes 

 oblique divisions may take place, so that a considerable bulk of 



