1 6 CALIFOKMIA ACADEMY OF SCIE\rCES. [Proc. 3U Ser. 



two resulting cells separate, and it is not quite certain whether 

 up to the time they pass into the pollen-tube they still retain 

 the cell wall. The generative nuclei are extremely small 

 and stain much more strongly than the vegetative nucleus, 

 which remains permanently undivided. With the growth of 

 the ripening pollen-spore, there is a great increase in the 

 granular contents. Finally, a great amount of starch is de- 

 veloped, which renders the pollen-spores quite opaque (figs. 

 25, 26). 



The fully developed male flower of Naias jlexilis (figs. 

 27, 28) has a pedicel nearly equal in length to the flower 

 itself. The mature anther, whose wall consists now of little 

 more than a single layer of epidermal cells, is also surrounded 

 by the integument, whose upper part is developed into swollen 

 lobes, which open finally to allow the escape of the pollen 

 (fig. 28). The lower part of the integument is very much 

 compressed. The outer envelope is prolonged above the 

 summit of the anther and its apex terminates in a number 

 of brown teeth, very much like those of the carpellary en- 

 velope of the female flower. When the spores are to 

 be shed, there is a rapid growth of the filament, by which 

 the anther is carried up and breaks through the outer en- 

 velope laterally, and assumes a nearly horizontal position. 

 This does not correspond with the description of this species 

 given by Magnus (1870, p. 23, PI. II, figs. 28, 29), who 

 describes and figures it as having the anther pushing through 

 the apex of the outer envelope. All the specimens exam- 

 ined by the writer, however, were of the type given. Of 

 the species examined by Magnus (1870, p. 25), only one is 

 mentioned as having this form of dehiscence, viz., N. teimi- 

 folia R. Br. The pedicel of the flower, also, found by the 

 writer regularly in N. Jlexilis, was not observed in this 

 species by Magnus, who expressly states that the only 

 species with stalked flowers \s, JV. ^odostemon (Magnus, 1870, 

 p. 24). 



The anther in JV. Jlexilis has, as we have seen, but a 

 single loculus, corresponding in this respect to most of the 

 other species. JV. major (Magnus, 1870, p. 22), however. 



