298 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Srr. 



the ripe spore a structure which closely resembles the small 

 vegetative prothallial cell in the germinating microspores of 

 such heterosporous Pteridophytes as /socles and Selaginella. 

 Chamberlain (1895) speaks of such a prothallial cell as an 

 occasional occurrence in Lilium Philadclphicum, but except 

 for this reference I am not aware of any reference to such a 

 structure in the angiospermous pollen-spore. This prothal- 

 lial cell, if such it is, in Sparganium simplex is lenticular 

 in form (fig. 6), and separated from the body of the spore 

 by a very well defined membrane which stains strongly with 

 Bismarck-brown. While it was not possible to demonstrate 

 positively the presence of a nucleus in this cell, there was 

 usually to be seen a central body which stained more deeply 

 than the rest of the cell with the usual nuclei stains and had 

 much the aspect of a partially disorganized nucleus. While 

 it seems very likely that this really represents a prothallial 

 cell, homologous with the similar one in the microspores of 

 Isoetes, for instance, its real nature cannot be positively as- 

 sumed until its history has been followed. 



The stamens of S. Greenii closely resemble those of S. 

 simplex, but the pollen-grains did not show any trace of the 

 prothallial cell, and the epispore is marked with fine reticu- 

 lations. At one point (fig. 7) these were absent, and the 

 clear area probably marks the point at which the pollen- 

 tube emerges. 



The Pistillate Flower. 



The pistil may be composed of a single carpel, as in S . 

 simplex and S. longifolium, or of two completely united 

 ones, as in S . Greenii and S . enrycar-pum. In S . simplex 

 (fig. 3) a longitudinal section of the ovary shows the sin- 

 gle anatropous ovule pendent from the upper part of the 

 ovarian cavity. The narrow canal traversing the style 

 opens into the ovary close to the base of the funiculus of 

 the ovule. 



The funiculus is rather slender and has a single axial 

 vascular bundle. The nucellus is oval and there are two 

 integuments usually found in the ovules of Monocotyledons. 



