METHODS OF TESTING SPORE GERMINATION 213 



expressing the results of progressively changing treatments plotted 

 against germination of spores as a jagged curve, whereas this curve 

 should be smooth if a sufficient number of spores has been counted. 



In regard to faulty technique it is essential that such environ- 

 mental factors as temperature, time, nature of the medium used 

 in germination, and cleanliness of glassware be controlled. More- 

 over, uniformity of source and age of spores and density of spore 

 suspension should be given attention. Repetitions of tests on 

 different days may yield variations whose causes are not well 

 understood. 



In connection with differences in results between duplicated 

 germination tests, it is possible to determine whether these differ- 

 ences are real and also to compute the degree of significance of 

 differences. Differences attributable to variations in sampling have 

 been found to follow a mathematical law. By use of a formula, 

 that is, by making the Chi-square test (X 2 ), and by reference to 

 the tables of Fisher (1930, pp. 75-98), which give the probability 

 of occurrence of such values of X 2 , the variations caused by errors 

 in sampling can be evaluated. The procedures involved in these 

 computations are not complicated, although detailed explanation 

 of them is wholly beside the purpose of this chapter. 



Some fungi do not seem to require that energy-yielding ma- 

 terials be present for germination, as noted by Lin (1940), using 

 conidia of Sclerotinia fructicola. Other species, however, are 

 found dependent upon the presence of sugars and minerals. Lin 

 (1945) demonstrated that the conidia of Glomerella cingiilata re- 

 quire carbon, magnesium, nitrogen, and phosphorus. He supplied 

 carbon as dextrose in 0.01% solution and minerals in 1.0 millimols 

 with the results shown in Table 16. 



TABLE 16 



Nutritional Requirements for Germination of Glomerella cingulata 



Substance Supplied 



Redistilled water 



Dextrose 



KXO3 + KH2PO4 + MgS0 4 



Dextrose + KNO3 + KH 2 P0 4 + Na 2 S0 4 



Dextrose + KXO3 4- KC1 4- MgS0 4 



Dextrose + KC1 + KH 2 P0 4 4- MgS0 4 



Dextrose + KNO3 4" KH 2 P0 4 4" MgS0 4 



