360 BOTANICAL GAZETTE [November 



cilia. He considered the latter number the typical one, while 

 Petersen (4) has described the zoospores as uniciliate. 



The zoospore contains a large subtriangular centrally located 

 body which resembles a large nucleus (fig. 23). Thaxter observed 

 this body and described it as follows: "The nucleus is very large 

 and subtriangular in outline, its base connected with that of the 

 cilia by a fine strand of protoplasm. " Fig. 24 shows very distinctly 

 the connection of the cilium with the base of the large central body. 

 The zoospore was killed with a 1 per cent solution of osmic acid and 

 stained with an alcoholic solution of Magdala red. In the process 

 the outer portion of the zoospore broke away, leaving the cilium 

 still attached to the central body as represented. There can be 

 observed in properly killed and frequently in living zoospores a 

 more or less hyaline globule situated at the base of the central body, 

 which contains a highly refractive granule. This body is undoubt- 

 edly the nucleus of the zoospore and will be more fully discussed 

 later. The zoospore also contains groups of large and small 

 granules, evidently of a fatty nature, which are principally located 

 in front and to the rear of the so-called central body. 



In movement the zoospores proceed in a more or less direct 

 course, with a slight swaying of the body, and at times accompanied 

 by a slow rotation on the longitudinal axis. If supplied with 

 sufficient oxygen they may continue to swim for a number of hours, 

 but when mounted on a slide under a cover glass, where the oxygen 

 supply is small, they soon cease movement and germinate. 

 . Fig. 28 shows a section of a young reproductive body, pre- 

 sumably a young sporangium, stained with iron-alum hematoxylin. 

 The protoplasm is granular, vacuolated, and contains distributed 

 throughout it prominent nuclei and large and small deeply staining 

 bodies to which reference has already been made.. The number of 

 nuclei is at first small, and there is apparently no marked passage 

 of the nuclei from the adjacent portions of the mycelium such as 

 occurs in the developing sporangia and sexual organs of many 

 other Phycomycetes. The nuclei in the upper half of the sporan- 

 gium are in various stages of division. This condition may be 

 found in young rapidly growing hyphae and principally at the grow- 

 ing point. As growth proceeds the number of nuclei rapidly 



