38 MINNESOTA BOTANICAL STUDIES. 



paraphyses were observed projecting out of the ostiole, but not 

 very much, only two or three cell lengths. 



Reproductive organs. The oogonia and the antheridia 

 appear at about the same time. Pelvetia fastigiata has herma- 

 phrodite conceptacles, and it is impossible to say that the oogonia 

 or antheridia have special parts of the conceptacle on which to 

 grow. Both may be found anywhere, except that the anthe- 

 ridia do not seem to develop as close to the ostiole as the oogonia 

 sometimes do. Both organs arise in the same way as para- 

 physes, as buds from the cells that line the conceptacle. 



Oogonium. The oogonium may be recognized from the 

 beginning by the fact that the cell which forms it from the first 

 has darker contents than the rest of the cells in the conceptacle 

 wall (PL XII., Fig. 36]. The young oogonia also are darker. 

 The contents of the oogonial mother cell are composed of a 

 very granular protoplasm. The oogone arises as a swelling 

 along the whole free surface of the mother cell. Paraphyses 

 and antheridial hairs do not occupy so much of the free wall 

 of the mother cell. In other words, they start as mere slender 

 buds. After extending into the conceptacle a distance a little 

 greater than the thickness of the mother cell, a dividing wall is 

 laid down, thus forming the oogone and its basal cell (Figs, 31 

 and 32). This wall is evidently porous, as the protoplasm of 

 both cells seems to communicate through it. The pedicel for 

 some time retains the opacity of its contents but later becomes 

 more like the other cells in the conceptacular wall. 



The oogonial cell continues dark, increasing in opacity as it 

 matures. This fact, together with the other fact that the fixing 

 and preservation in formalin is not a good way to prepare these 

 tissues for cytological study, in truth seems to make staining 

 more difficult. For this reason it has been impossible to carry 

 out the study of the development of the oospheres in a satisfac- 

 tory manner. It was found, however, that if the sections were 

 bleached from fifteen to twenty minutes in chlorine gas, stained 

 in haematoxylin for twenty-four hours, and washed in acid 

 alcohol till the stain of the other tissues was nearly removed, 

 then the nuclei of the oogones could be seen. Methyl violet 

 and acid alcohol also brought out the nuclei. In younger and 

 more transparent oogones the nuclei can be made out without 

 bleaching. In this way the oogone was traced from the uninu- 

 clear to the four-nuclear stage (Figs. 3136). Thuret states 



