THE BUD-ROT OF PALIMS TN TNDTA. 2y>:] 



types of germination occur, which thougli distinct enough in appear- 

 ance, are all modifications of the one process. The most character- 

 istic, though by no means the most common, is that wliicli is practic- 

 ally universal in the genus Pythium and which is, as pointed out 

 in the general account of the genus previously referred to, the only 

 absolute mark of distinction of this genus from Phytophthora. In 

 this case the apex of the papilla swells up into a very thin gelatinous 

 vesicle into which the protoplasm of the sporangium passes in a 

 uniform granular mass. Within the vesicle it segments to form a 

 number of zoospores, which develop cilia and move ever more vig- 

 orously in the confined space, until the vesicle wall ruptures and 

 the spores swim of! in all directions (plate IV, figs. 6 and 7). In 

 some cultures prolonged search was necessary to find instances of 

 this type of germination ; in others it was quite common. On the 

 whole it is less frequent in the cooler months of the year than that 

 next to be described. 



This is simply an incomplete form of the last, in which the vesicle 

 is either not formed at all, the apex of the papilla dissolving, or if 

 formed, ruptures almost immediately. Segmentation into zoospores 

 occurs within the sporangium, and is complete or nearly complete 

 before the papilla opens. As soon as an opening forms, the proto- 

 plasm streams out and breaks up at once into free swimming zoo- 

 spores (plate IV, fig. 8). Owing to the pressure of the mass within 

 the sporangium it is not possible to distinguish the indi\'id\uil zoo- 

 spores before escape, but it is evident that they must be fully formed 

 before the rupture of the papilla since they separate at once after 

 escape, and also because as soon as pressure is reduced by the extru- 

 sion of part of the sporangia! protoplasm, the remaindei- may seg- 

 ment while still inside and emerge as fully formed mature zoospores. 

 This is the type of zoospore formation habitually met in Phytoph- 

 thora, and in several cases the palm parasite would have been taken 

 for a Phytophthora, had not prolonged search revealed an occasional 

 instance of the first type of discharge. Intermediate types between 

 the two are sometimes found. Thus in one case about three-quar- 

 ters of the protoplasm emerged in a mass surrounded by a vesicle, 



3 



