422 H. MAESHALL WARD. 



In one instance (fig. 8) tliis took place at the end of each of 

 the two branches. The protoplasm of the original conidium 

 passed entirely into the hypha, and along it (fig. 7) wholly 

 into the new or secondary conidium, which is usually somewhat 

 smaller and sometimes much smaller (fig. 8) than the primary 

 conidium. One or two fine transverse septa may be formed iu 

 the germinal hypha (fig. 7). As a very general rule the 

 secondary conidium is oblique or misshapen ; fig. 7 was an ex- 

 ceptionally symmetrical one. 



The conditions which determine this mode of germination, 

 in preference to the formation of zoospores directly, are not 

 quite clear ; but they seem to be connected with the nutrition 

 of the germinating conidium. When the sowings of conidia 

 are exposed to light these secondary conidia are often formed ; 

 and I found it more difficult to obtain the zoospores in well-water 

 than in rainwater. I here speak more especially of water from 

 a particular well, which has proved to contain considerable 

 quantities of organic matter. In large sowings, i. e. where 

 eighty to hundred or more conidia existed in the drop of water, 

 by far the majority of the conidia germinated in this manner; 

 and wherever the germination was delayed from obscure causes 

 beyond twelve hours, this was the prevalent form it assumed. 

 Sowings in very dilute infusions of organic matter (jam and 

 horsedung were tried) never yielded zoospores, whereas several 

 conidia would germinate like this. When large quantities of 

 the conidia were sown on a small area of the potato leaf or 

 stem, a larger portion of them germinated thus (see fig. 9, 

 below). No connection was established between differences of 

 temperature and of mode of germination. Putting all these 

 facts together, it seems not improbable that the difference is 

 due to nutrition, and possibly three factors were concerned in 

 affecting this, (1) the amount of free oxygen available, (2) the 

 comparative maturity of the conidia themselves, and (3) the 

 intensity of the light. It is not inconceivable that direct sun- 

 light increases the oxidizing processes during the early stages 

 of the germination ; and I feel convinced that the presence of 

 numerous competing conidia, or of organic matter generally, 



