42 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



in the sporogenous tissue. The latter is not clearly delimited 

 in longitudinal sections, but in transverse sections the four 

 groups of sporogenous tissue are more clearly defined. 

 The structure of the anther at this stage shows nothing 

 peculiar. As the stamen grows older the superficial cells 

 have their walls thickened and are quite different in appear- 

 ance from the cells beneath them (fig. 89). The sporo- 

 genous cells are now better marked and show the larger 

 nuclei and denser contents usual in similar cells. Surround- 

 ing the masses of sporogenous cells are about three layers 

 of cells forming the tapetum. These, as usual, are almost 

 completely absorbed when the anther is mature. No especial 

 study of the development of the pollen was made, as there 

 seemed to be no peculiarities worthy of note, except the 

 fact that not all the sporogenous cells give rise to spores; 

 but a certain number are broken down and their free nuclei 

 can be observed among the young spores (fig. 91, 3). This 

 recalls the similar behavior of the sporogenous cells of Equi- 

 setuni. The pollen-spores are small globular cells, which 

 contain two nuclei at maturity, a large vegetative nucleus, 

 and a small generative one contained in a separate antheri- 

 dial cell (fig. 91)- Like the pollen-spores of Naias, no exo- 

 spore is developed, and the ripe spore contains numerous 

 starch granules. 



A striking feature of the stamen is the development of its 

 apex into a prominent appendage made up of large cells 

 (fig. 90). The filament is traversed by a vascular bundle, 

 which has a strand of tracheary tissue, showing in section 

 usually two tracheids. 



V. The Female Flower. 



The pistillate flowers of Zannichellia form a cluster at the 

 end of a short branch, the whole inflorescence being sur- 

 roundedby a bell-shaped envelope of membranaceous texture, 

 very like the similar sheaths below the nodes of the main 

 axis. Botanists usually regard this whole carpellary com- 

 plex as a single flower, and Magnus (1894, p. 223) compares 



