fl . VVORMALD 



97 



making any definite directive movement. In another instance two 

 zoospores appeared to be attached by their cilia for a dehcate fibril 

 was seen to be connecting them; by their frantic efforts this was soon 

 broken and they disappeared in opposite directions. 



Frequently fragments of protoplasm remained just outside the mouth 

 of the sporangium after the zoospores had swum away; these became 

 rounded oH and showed no signs of movement. The zoospores after 

 swimming about for some time lost their motility, assumed a spherical 

 form and began to germinate, each producing a single germ tube. 



The vesicle which is produced when the zoospores are liberated from 

 a sporangium is transparent and only just visible during the short time 

 taken in its expansion : it is produced so rapidly and is so very evanescent. 



Fig. 2. A sporangium from which the zoospores cmciged slowh'; the orientation of the 

 cilia was seen under those conditions. 



disappearing from view while more than half the zoospores are still 

 within the sporangium, that it may easily escape notice, and is probably 

 of more general occurrence than is usually supposed to be the case. The 

 observations here recorded were made in the summer of 1913. In the 

 same year Dastur(2) recorded and figured the vesicle for Phytophthora 

 parasitica; Rosenbaum(iO) in 1917 recorded having observed it in P. 

 Cadorum, P. Arecae and P. jxirasitica and quite recently Pethybridge 

 and Lafferty(8) have observed it in P. cryptogea. On the other hand 

 Robinson (9) states that he has never observed it in the Phytophthora 

 which he found associated with a Wilt Disease of Asters and assumes 

 that the absence of the vesicle is a characteristic of the genus dis- 

 tinguishing it from Pythium. 



