SPORE GERMINATION 361 



secondary one between G.O and 7.0. Of all the media tested, beet decoc- 

 tion gave the maximum germination imder the widest range of conditions. 

 Webb also clearly demonstrated that the range of pH favoring germina- 

 tion is influenced by temperature and by the constituents of the medium. 



All the species of Myxomycetes studied by Smart (1937) germinated 

 within a pH range of 4.0 to 8.0. Spores of Fuligo septica germinated 

 from pH 2.0 to 10.0. Optimum for all species ranged from 4.5 to 7.0, 

 with some germinating better near 4.5 and others near 7.0. The spores 

 of Urocystis occulta germinated between pH 5.0 and 8.9, with the optimum 

 at 6.8 (Ling, 1940). This optimum is higher than those for most fungi. 

 Kauffman (1934) found the range for spore germination of several species 

 of Basidiomycetes (Agaricaceae and Nidulariaceae) to be pH 5.0 to 8.5 

 with the optimum near 7.5. 



It is interesting that Doran (1922) in his review of spore germination 

 makes no mention of acidity as a factor. It would appear that acidity 

 is of more or less importance as a modifying factor, even though it is 

 seldom a limiting factor for spore germination. This may explain, at 

 least in part, the fact that we often find abundant ungerminated spores 

 in fruiting liquid cultures. Some fungi sporulate only in neutral or 

 alkaline media, which, in general, are not favorable to spore germination. 



NUTRIENTS AND STIMULANTS 



The constituents of the substrate are known to influence spore germina- 

 tion of some species of fungi. Some species germinate well in distilled 

 or tap water, while others require certain special nutrients such as sugar, 

 salts, or even a particular nitrogen source. No one medium has been 

 found which will allow good germination of all fungi, although certain 

 natural media, such as beet or bean decoction and soil infusion, seem to 

 favor germination in a large number of fungi. When such media con- 

 taining natural products are used, it is difficult to determine whether the 

 higher percentage of spore germination is due to the nutrients or to some 

 stimulant which is not used in the metabolism of the fungus. 



Duggar w^as one of the foremost American workers interested in spore 

 germination as a primary subject of experimentation. Prior to his work, 

 most of the study on spore germination was only incidental to other 

 problems. Duggar (1901) demonstrated that species differ in their 

 nutrient requirements for germination by placing spores in water, bean 

 decoction, nutrient-salt solution, and cane-sugar solution. A portion of 

 his data showing the percentage of germination after 15 hr. is given in 

 Table 59. 



Among some of the compounds Duggar found to influence sporulation 

 of Aspergillus flavus and A. niger were varying amounts of peptone, 

 ammonium nitrate, and magnesium sulfate. Ammonium nitrate at a 



