THE BUD-ROT OF PALMS IN INDIA. 255 



zoosporal method, while most can also germinate by germ-tubes. 

 In the higher Peronosporaceae the formation of zoospores gradually 

 disappears and direct germination becomes the rule. Plate IV, 

 figs. 10 and 11, show direct germination of the sporangia of Pythium 

 palmivorum. In many cases the germ-tube is single and arises 

 from the papilla at the apex of the sporangium (fig. 10). In others 

 a number of germ-tubes arise scattered over the surface (fig. 11). 

 Usually the growth of the germ-tubes is limited, and secondary spor- 

 angia are early formed at their apices and those of their branches 

 (fig. 10 b. c. d.). 



The zoospores are of the ordinary Pythium type, and measure 

 from 8 to 10 ij- after they come to rest and assume a spherical shape. 

 They germinate rapidly (within an hour) by one or sometimes two 

 germ-tubes, which may grow to a considerable length and branch 

 (plate IV, fig. 12). Sometimes they fail to germinate and break up 

 into a granular mass (plate IV, fig. 13). In a few cases two or more 

 spores remain united after leaving the Sporangium. These double 

 zoospores are marked by their large size, and instead of becoming 

 spherical at the end of their period of swarming, assume an oval 

 or irregular shape, and are surrounded by a single wall (plate IV, 

 fig. 14), Germination in these cases is quite normal. In one in- 

 stance the whole contents of the sporangium escaped in a mass and 

 moved about with an irregular jerky motion, eventually coming to 

 rest and forming a common wall. Germination was not seen. 



The second spore form is that which was termed an oospore 

 in the previous description. Further examination has shown that 

 it is not a sexual product and is not contained in an oogonium, but 

 is a distinct " resting " variety of conidium. At certain periods of 

 the year, e.g., in the hot dry weather in March, only this spore form 

 has been found. In other cases it has been found on the same my- 

 celium as the sporangia, and there is no doubt of its bein<y a stage 

 of Pythium palmivorum. The resting spores are spherical, thick- 

 walled, often yellowish when old and are formed singly at the ends 

 of usually large hyphae (plate V). Intercalar ones have occasional- 

 ly been observed (plate V, fig. 7). They measure from 25 to 40 u 



