94 



The Waterlilies. 



larger than single grains of some plants. Each spherule is surrounded 

 by a pellicle of protoplasm, and a network of the same substance 

 ramifies among the constituent granules. This type of aggregation 

 exists in a less perfect condition in N. jiava, but was not seen elsewhere. 

 In N. odorata stained sections of the perisperm show a network of 



thicker plasma strands between the starch 

 spherules near the middle of each cell. 



In the micropylar end of the seed a 

 small lenticular or globose space (Fig. 44) is 

 occupied by the endosperm and embryo. 

 The former is a single layer of cubical cells 

 (e) inclosing the latter. The endosperm cells 

 are thin-walled, but Weberbauer was able to 

 find the walls covered with pits so that the 

 thicker portions formed a fine network. They 

 have moderate nuclei, and contain a rich 

 supply of proteids and oil, but no starch. 

 Over the radicle the endosperm is very thin 

 and poor in contents. The embryo has two 

 equal, fleshy, hemispherical cotyledons, ex- 

 cavated on the inner side to receive the 

 plumule. Between their symmetrical bases 

 is the tiny caulicle, and a slight prominence 

 at the end of this is the radicle. Food- 

 storing tissue of isodiametric cells and elongated conducting cells are 

 distinguishable ; an axial strand of the latter is found in the caulicle, 

 with a branch into each cotyledon. No starch is found in the embryo, 

 but it is richly supplied in all its parts with oil and protein. In a 

 crushed embryo of N. flava the oil globules run together in considerable 

 drops which stain easily with alcannin. The plumule consists of two 

 rounded papillae, the leaf rudiments, placed transversely to the cotyledons. 

 One of these is about four times as large in volume as the other. 



Fig. 44. Longitudinal section of seed : 

 c, cotyledon ; e, endosperm ; g, tegmcn ; 

 m, micropyle ; p, perisperm ; I, testa. 



