2 9 6 BOTANICAL GAZETTE [may 



in this material and the results were published in the preceding 

 papers (81, 82). 



In a number of pots placed in saucers filled with water like the 

 rest, watering from above was avoided and the cultures were exposed 

 to direct sunlight after the prothallia had developed two or three 

 cells. The excessive evaporation from the soil was regulated care- 

 fully, so as not to permit condensation on the prothallia, and allow fer- 

 tilization. Thus the prothallia were kept growing for a long period 

 in dryness and in exposure to direct sunlight, the temperature of the 

 room being kept at 28°-32° C. No fungi or lower algae developed 

 in the pots. 



The rate of growth of these prothallia when compared with that 

 of those placed in normal conditions was quite slow. Antheridia 

 appeared earlier than under normal conditions and were very numer- 

 ous. About five or six weeks after the prothallia of two or three 

 cells were examined, there was observed a peculiar thickening in the 

 cushion region of some of the prothallia which reached the cushion 

 condition earlier than the rest. This thickening was determined 

 afterward to be the initiation of an apogamous sporophytic outgrowth. 

 During the next three or four weeks the growth of the sporophyte 

 was rather rapid, and at the end of that time it had become leafy. 

 Fixation of the prothallia was made during all stages of development. 



The killing and fixing of the material, with washing, imbedding, 

 cutting, and staining, were done by the method used in the study of 

 spermatogenesis, oogenesis, and fertilization. 



This investigation was begun in October 1906, at the suggestion 

 of Professor John M. Coulter and Dr. Charles J. Chamberlain, 

 and I wish to express my sincere gratitude to these gentlemen for 

 their kind advice and criticism. I am also under obligation to the 

 other members of the botanical staff for many courtesies. 



Description of the apogamous prothallia 



VEGETATIVE MITOSIS 



The prothallia which produce sporophytic outgrowths apoga- 

 mously do so under the influence of artificial culture. The mitoses 

 which occur up to the 30-50-celled stage are exactly similar to those 

 in normal prothallia, but beyond that stage the morphological struc- 



