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



vent the pollen-spores falling out spontaneously, will not 

 hold for N. jlexilis, nor has the writer observed in this 

 species the pollen germinating within the cavity of the open 

 anther as Magnus (1. c.) found to be the case. 



Germinating spores were found in abundance upon the 

 stigmas of the mature flower. The pollen-grains were held 

 between the stigmatic lobes and in some cases seemed to 

 adhere to the style, possibly by a secretion of the stigmatic 

 cells. The germination is probably entirely at the expense 

 of the spore contents and no nutriment is apparently received 

 from the stigmatic cells. The tube quite as often grows 

 down on the outside of the style as between its lobes. Some 

 of the pollen-tubes, however, penetrate into the canal of the 

 style and make their way into the ovarian cavity. After 

 reaching this, it is extremely likely that they are nourished 

 by the secretion of the papillae at the lower opening of the 

 canal, which seems to fill the cavity of the ovary. The 

 exact course of the tubes was not traced, as they are not 

 easily seen in sections; but probably the course follows the 

 inner wall of the ovary until the group of papillae at the 

 opening of the micropyle directs the growth of the tube 

 into the micropyle itself. The end of the pollen-tube, where 

 it was found on the outside of the style (figs. 32, 33), was 

 usually slightly swollen and contained dense, finely granular 

 protoplasm, in which, in favorable cases, could be seen the 

 two, small, generative nuclei. In none of those examined 

 could the vegetative nucleus be seen with any certainty. 

 In the germinating spores the outline of the pollen-spore 

 was retained, but all the granular contents had passed into 

 the tube and mostly disappeared as the tube lengthened. 



VI. Fertilization. 



The penetration of the pollen-tube into the embryo-sac 

 was seen in several instances, but the nuclear elements are 

 too small to make this a specially favorable subject for the 

 study of the phenomena of fertilization and no very de- 

 tailed investigation was made. 



