424 BULLETIN' 387 



culties, Eycleshymer (1894) not only found swarm-spores, but also found 

 that when left in the culture for a few days these apparently fused 

 into larger bodies, thereby reacting in much the same manner as Kunkel 

 (1915) found to be the case with Spongospora subterranea (Wollr.) 

 Johnson. Kunkel discovered that each cell of a spore ball produces a 

 single uninucleate amoeba which soon fuses with others of its kind to 

 form a small plasmodium. This occurs not only in the case of spores in 

 the soil, but even with those still in the base of the old sorus. 



There are several obstacles to be encountered in trying to observe the 

 actual emergence of the protoplasmic mass from the old spore wall. First, 

 it is difficult to get a very large percentage of germination unless the most 

 favorable conditions are present. Secondly, all observations must be made 

 with the oil-immersion objective. When the protoplasm is about half- 

 way out, the spore wall and the emerging protoplast begin to move, making 

 it hard to keep them in focus or even within the field. Consequently, 

 when the process seems almost complete there is a sudden swift whirl, 

 and the swarm-spore, with the adhering empty wall, darts out of sight. 

 When located again, the spore wall is empty, and the swarm-spore, lost 

 among others, is impossible of identification. For this reason no actual 

 separation of the protoplasm from the spore wall has been seen, but 

 enough of the process has been observed to enable investigators to deter- 

 mine the general method by which this is accomplished and to be sure 

 that a spore gives rise to only one swarm-spore. 



It was soon learned that spores do not germinate well, if at a 1 !, in dis- 

 tilled water, and further that, altho from one to five per cent of the spores 

 taken directly from a fresh root germinate in muck-soil filtrate, a much 

 larger percentage of germination can be obtained by exposing the roots 

 to freezing temperatures for two weeks or longer. This was accomplished 

 by tying the roots in cheesecloth and burying them under the snow, or 

 in summer by keeping them in the refrigerator for that length of time. 

 Drying the roots also seems to have a beneficial effect on germination, 

 altho this must not be carried to the extreme. The muck-soil filtrate 

 was made by filling an ordinary flowerpot with muck, placing it over a 

 large funnel lined with filter paper, and then pouring hot water on the 

 soil. The resulting medium was of an amber color and slightly acid. 



Temperature conditions also influence germination of the spores. It 

 was practically impossible to obtain infection in the greenhouse during 

 the coldest winter months when the temperature was from 10 to 18 C. 

 The spores also fail to germinate at ordinary room temperature (from 1 6 

 to 21 C.). The optimum temperature for germination proved to be from 

 27 to 30 C. This, however, is not the case when spores are placed in 

 test tubes on agar with young cabbage seedlings, for under such conditions 



