228 GERMINATION OF SPORES 



and remain dormant throughout winter. The ascogenous stage of 

 a third group develops slowly during winter and matures in 

 spring. In any event the overwintering of conidia of a species 

 not known to possess an ascogenous stage is not a criterion upon 

 which to predicate the possession of such a stage. 



Temperature and percentage germination. Obviously the 

 proportion of the total number of spores of a given species which 

 (terminate is correlated with temperature and with time as external 

 factors of primary importance. Temperature as a correlated 

 factor in percentage germination is illustrated by the observations 

 of Kaufmann (1934), presented in Table 21. Germination was 



TABLE 21 



Proportion of Spores of Certain Basidiomycetes That Germinate at 



Different Temperatures 



Percentage of Germination at 



relatively poor with each of these species, so that the relationship 

 is not so striking as may have been desired. Doran's (1922) re- 

 sults with a series of trials employing conidia of Venturia inaequa- 

 lis are more representative. The averages of his tests are 0% at 

 2° C, 3% at 5° C, 21.5% at 8° C, 56.2°fat 10° C, 76.5% at 12° C, 

 100% at 15° C, 77.2% at 18° C, 56.5\ at 20° C, 41.5% at 24° C, 

 22.2% at 28° C, 11% at 30° C, and 0% at 32° C 



Time required for germination at different temperatures. 

 As has previously been stated, the spores of some fungi are capable 

 of germination as soon as they are produced, whereas others un- 

 dergo a period of dormancy. In any event temperature is a factor 

 correlated with the time required for spore germination. In some 

 species germination can be secured within an hour; at the opposite 

 extreme, others may require exposure for several weeks to condi- 

 tions favoring germination. The time-temperature relationships 

 in spore germination are illustrated by Ames's (1915) results of 

 studies on fruit-rottino- funm and are shown in Table 22. 



