232 GERMINATION OF SPORES 



but ^Termination was inhibited under the red, orange, yellow, and 

 purple filters. 



INFLUENCE OF NUTRITION ON GERMINATION 



As has been emphasized, the intake of water by the spore is the 

 sine qua 11 on for the initiation of germination. Apparently, how- 

 ever, not all species can be made to germinate in pure water. 

 Since water is a universal solvent, spores do not come in contact 

 with pure water under natural conditions. Whether they lodge 

 on living plants or animals, on decaying tissues, on the soil, or in 

 water, thev come in contact with soluble organic materials. Ad- 

 vantage may be taken of this fact in germination trials, especially 

 with species that thus far have proved impossible to grow in arti- 

 ficial culture, for example, Peronosporaceae, Erysiphaceae, and 

 Hvpodermataceae. The germination of some species in those 

 families appears to be hastened by the presence of the green tissues 

 of their appropriate hosts. Similar experiences have also been 

 recorded with Rhytisma acerinum, Gnomonia ulmea, Cymadothea 

 trifolii, Diplocarpon rosae, and Lhwspora gleditsiae. Germination 

 of the spores of Merulius lacrymans is hastened by the presence 

 of urine. In general, with species whose germination is attended 

 with difficulty in potable water, an attempt should be made to 

 approximate natural conditions of germination. 



RESUME 



It is plainly apparent from the foregoing discussion that both 

 hereditarv and environmental factors influence the germination 

 of fungus spores. It is not evident, however, that anything of 

 fundamental importance is likely to be established by additional 

 studies of this sort involving either these same species or other 

 species. Perhaps attention might better be centered on determin- 

 ing the causes of dormancy in spores and the means whereby dor- 

 mancy may be broken. Such inquiries are likely to be most fruit- 

 ful if they are patterned after studies on the germination of seed. 



Studies involving the presence of growth factors to hasten or 

 to increase germination might conceivably yield results of value, 

 especially with species that require the given growth factor for 



