i9"] BARRETT— BLASTOCLADIA 363 



blackened condition of the granules, which indicates their fatty 

 nature. 



Papillae of dehiscence occur on the zoosporangia of many 

 Phycomycetes. In most cases they have been described as small 

 swollen areas in the sporangia! wall, or tips of exit tubes which 

 become gelatinized and allow the emission of the zoospores to take 



place. 



Rhipidium 



The zoosporangium possesses a double wall; the outer forms a cap 



which 



lifted up by the protruding inner wall; the latter forms a cylinder 



which 



it ruptures 



them free (Thaxter 10). A similar 



Sap 



So far as I have been able to learn, the structure and behavior 



differ 



sporangium 



an outer highly refractive hyaline convex cap, with a less refractive 

 area between it and the protoplasm of the sporangium. The 



more 



proceeds (fig. 8). Just before the disappearance of the outer part 

 it loses its high refractive power to some extent, and has the sem- 

 blance of glycerine. Suddenly the thin ungelatinized portion of the 

 wall breaks, and becomes forced out, leaving a ragged rim, many 

 times, about the opening. The adjacent gelatinized part is 

 diately dissolved in the surrounding water, and to all appearances 



imme 



begin 



the exit pore is open. 



escape. Under what seem to be normal conditions, a vesicle is 



formed which incloses at least a part of the zoospores on their 



discharge. This vesicle soon breaks and the zoospores are set 

 free (fig. 13). _ _ 



The formation of 



b 



in 



immediately 



zoosporangium 



Rhip 



its gelatinization it was enabled to stretch out in the form of a 



thin 



sac. 



examination 



