366 PHYSIOLOGY OF THE FUNGI 



Distillates of these leaves increased germination four to ten times. Ethyl 

 acetate likewise gave similar results. The possibility of specific activity 

 was suggested by the fact that apple tissues distinctly stimulated germina- 

 tion of B. cinerea spores, while they inhibited germination of spores of 

 Colletotrichum lindemuthianum. The stimulation was greater with old 

 spores. 



Presoaking and the subsequent addition of a stimulating volatile agent 

 gave optimum germination of Urocystis tritici spores (Noble, 1923). 

 The expressed sap of wheat placed in the same container with germinating 

 spores, but in separate dishes, proved to be a good stimulating agent. 

 Uninjured seedlings of certain nonsusceptible hosts likewise stimulated 

 spore germination. Benzaldehyde, salicylaldehyde, butyric acid, and 

 acetone in certain concentrations stimulated germination of presoaked 

 spores. Noble believed that presoaking increased permeability of the 

 spore and allowed the more rapid intake of the stimulatory volatile sub- 

 stance, which increased the permeability of the protoplasmic membrane 

 by changing its physical condition. 



Likewise, a solution of benzaldehyde (3/2,000,000) stimulated germina- 

 tion of Urocystis occulta spores, which germinated very poorly in water 

 (Ling, 1940). Ethyl alcohol stimulated spore germination in Aspergillus 

 flavus; methyl alcohol was slower and less effective (Duggar, 1901). A. 

 niger was stimulated by oxalic acid, whereas .4. fiavus was not. It is 

 understood that the stimulatory power of these chemicals depends upon 

 the concentration. 



An interesting situation exists in the germination response of some 

 spores to the presence of other fungi, or even to the medium in which 

 other fungi have grown. The few experiments conducted along this line 

 suggest that the constant association with other organisms may be highly 

 beneficial to spore germination as well as subsequent growth of some fungi 

 in nature. 



The germination of a number of species of Myxomycetes was increased 

 by the addition of the filtrate of a medium in which spores had previously 

 been germinated (Smart, 1937). Smart calls the stimulatory factor an 

 "autocatalytic agent." A portion of Smart's data is presented in Table 

 62. 



Fries (1941, 1943) obtained almost phenomenal results with spores of a 

 number of Hymenomycetes, which previously had germinated poorly 

 or not at all, by sowing the spores on malt agar with living cultures of 

 Torulopsis sanguinea. Spores of ten species of Tricholoma, which ger- 

 minated only with difficulty without the yeast, were found to germinate 

 readily in its presence. One species of Tricholoma gave only negative 

 results. In Amanita mappa, A. porphyria, and A. rubescens germination 

 occurred only when Torulopsis was present. Germination of two other 



