152 



Mycologia 



appears to be a stage prior to the enlargement and fusion of the 

 vacuoles into a large central vacuole. 



Barrett (3) studied both living and stained material of a num- 

 ber of Olpidiopsis species. He reports that he could not detect 

 any signs of the protoplasmic heapings described by Butler within 

 the sporangium. If one studies the figures in plate 24, one Is led 

 to believe that Barrett did not find the crucial stages of spore for- 

 mation. This leads him to the erroneous conclusion that " frag- 

 mentation of the protoplasm is simultaneous." 



Kusano (33) investigated the life history and cytology of Olpid- 

 ium viciae. He was unable to find evidence of progressive divi- 

 sion, but states " that a clear space appeared in the cytoplasm all 

 at once between each two nuclei, and that the protoplasm was cut 

 up into as many polygonal parts as there were nuclei." It seems 

 obvious that this statement refers to the stage following what 

 Strasburger and Biisgen regarded as a stage of coalescence of the 

 spore origins which is not real, but only apparent. 



The stages in the life history of Olpidiopsis saprolegniae, prior 

 to the formation of spores, have been discussed and figured by a 

 number of authors. From a study of the living material, in hang- 

 ing-drop cultures, I am able to confirm the existence of large cen- 

 trally disposed vacuoles in young sporangia, the increment in size, 

 and subsequent coalescence of these vacuoles. The process of 

 spore formation, as I have observed it, is entirely at variance with 

 that described by the above-mentioned authors. The phenomena 

 I observed were very similar to processes of spore formation in the 

 sporangia of Saprolegnia and A My a as I have found them and 

 not as described by Strasburger, Biisgen, and Hartog. I was able 

 to note the following changes by observing living specimens in 

 hanging-drop cultures. The history of one sporange is as follows : 



At 7 .-40 P.M. the sporange had a large central vacuole, and in 

 the median plane a blunt cleavage furrow could be seen extending 

 toward the periphery (text fig. A, 4). Three minutes later the 

 vacuole became irregular and one sharp and two blunt cleavage 

 furrows were visible (text fig. A, 5). Four minutes later the 

 vacuole had increased in size so that the protoplasm formed a 

 rather thin peripheral layer. Sharp cleavage furrows were now 



