300 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



small amount of material available, closely resembles that of 

 S. simplex, and as in that species there are but two, or at 

 most three, layers of cells at the apex of the nucellus. 



The common eastern S. exirycm'ftim , while resembling 

 more nearly S. Greenji, differs from it in some details. 

 The ovary is broader, due to an enlargement of the outer 

 cells, and there are numerous enlarged cells present which 

 contain bundles of rhaphides, or needle-shaped crystals, 

 presumably of calcium oxalate. These spicular cells also 

 occur in the placenta, and while not entirely absent from 

 the ovary of S. Greenii are much less abundant. There 

 are also found on the upper surface of the placenta papillate 

 cells which are much less marked in S . Greenii. These 

 are doubtless connected with the conduction of the pollen- 

 tubes. The structure of the ovule itself, and the embryo- 

 sac are much alike in the two species. 



In all the species examined the cells of the nucellus per- 

 sist, and the subsequent enlargement of the upper part of 

 the integuments and the apex of the nucellus gives rise to 

 the peculiar cap (" Samen-deckel " of Hegelmaier) which 

 characterizes the ripe seed of all species of Sparganimn. 



The broadly oval embryo-sac of S. simplex is scarcely at 

 all narrowed at either end. In all specimens examined the 

 two polar nuclei had already completely fused, and it is ev- 

 ident that the fusion of them to form the primary endosperm- 

 nucleus occurs some time before the fertilization of the 

 egg-cell. The large endosperm-nucleus (fig. 10) is im- 

 bedded in a considerable mass of granular cytoplasm which 

 is elsewhere confined to the thin parietal layer. The posi- 

 tion of the endosperm-nucleus is not constant, and it was 

 found in nearly all positions in the sac; sometimes it lay 

 close to the egg-apparatus, sometimes it was near the antip- 

 odal cells. 



The egg-apparatus is of the normal structure, and com- 

 pared to the size of the embryo-sac is small. A good deal 

 of variation in the size of the Qgg and synergidae was 

 noted, and these differences did not appear to be neces- 

 sarily connected with the age of the egg-apparatus. The 



