XII 



LEPTOSPORANGIA T.E HETEROSPOREJ-: 



415 



curvature is very pronounced, however, in the sporophyll, a 

 protuberance arises ui)on its inner face, a short distance above 

 the base (Fig. 216, A). This originates from a single cell, 

 which functions for some time as an apical cell, and causes the 

 young sporocarp to project strongly from the leaf, of which it 

 is simply a branch, somewhat analogous to the spike in 

 OpJiioglossuni. It has at first the form of a blunt cone, but 

 soon upon the side turned toward the leaf a slight prominence 

 appears (Fig. 216, B, L), and about the same time two similar 



k A 



D sf 



Fig. 216. — Pilularia Americana (A. Br.). Development of the sporocarp. A, Very young 

 sporophyll with sporocarp rudiment {sf), showing a distinct apical cell ; B-D, longitudinal 

 sections of young stages, showing the formation of the " sorus canals" {sc), X130; i', the 

 original apex of the young sporocarp ; L, secondary' lobes or leaflets; E, longitudinal section of 

 an older stage, X about 130; i-, s, young sori ; F, transverse section of an older sorus, XiSo. 



lateral ones are formed. As in the sterile joart of the leaf growth 

 is stronger on the outside, and the young sporocarp bends in 

 toward the leaf, so that the position of fertile and sterile 

 segments is very like that in the young sporophyll of OpJiio- 

 glossuni. The apex of the sporocarp rudiment, together with 

 the three lobes, enclose a slightly depressed area, which 

 becomes the top of the sporocarp. The four prominences 

 (including the original apex of the fertile segment) are beyond 



