194 CALIFORNIA ACADEMY OF SCIENCES. 



related Pilularia, and the segregation, even in the un- 

 germinated spore of the protoplasm which is to form the 

 prothallium. The spores are very large ellipsoidal cells, 

 about . 425 X. 750 mm. in diameter. They are ivory white 

 in color and covered with a slim}' mucilaginous coating of 

 considerable thickness. The upper end of the spore has 

 a hemispherical protuberance covered with an evidently 

 thinner brownish membrane, and it is the protoplasm 

 within this that alone gives rise to the young prothallium. 

 In cross sections it is plainly seen that the upper end of 

 this proturberance shows three radiating lines correspond- 

 ing to those at the apex of the microspore, and like them 

 indicates where the spore was in contact with the three 

 sister-spores in the mother cell. 



Sections of the ungerminated spore (pi. iv, tig. i), 

 show structures very like those in the microspore but 

 more strongly developed. The most noticeable differ- 

 ence is in the distribution of the contents. Instead of 

 having these uniform as in the microspore, here the pro- 

 toplasm filling the proturberance at the top is finely 

 granular and free from the large starch grains that occur 

 in the body of the spore. This dense protoplasm, too, 

 colors strongly with various staining agents, and the line 

 of demarkation is abrupt. The nucleus of the spore is 

 situated in the center of the apical protoplasm which, 

 however, is not separated by a membrane from the body 

 of the spore. The nucleus is more or less strongly flat- 

 tened, but this is exaggerated when the protoplasm at 

 the apex has contracted, as it often does during the pro- 

 cess of imbedding. The protoplasm of the body of the 

 spore is arranged reticulately and probably in the living 

 spore contains vacuoles and oily matter which is re- 

 moved in the process of imbedding. Granules of various 

 sizes, partly albuminous, and partly starch, are abundant. 



