6 BULLETIN 1053, U. S. DEPARTMENT OF AGRICULTURE.' 



tubes are formed, and the spore is always very conspicuous in the 

 thallus. The germ tubes of Fomes roseus have been more vacuolate 

 than those of the other species. 



The spores of all species germinate readily upon all nutrient media 

 and upon red spruce (PI. V, fig 10, for Lentinus lepideus). In water 

 the results were as erratic as those reported by other workers with 

 spores of basidiomycetes. The spores germinated in tap water, al- 

 though the proportion ranged from less than 1 to 55 per cent in dis- 

 tilled water germination took place occasionally (PI. Ill, fig. 2, for 

 Lenzites sepiaria). The rate of germination was usually low, 

 although sometimes as high as 50 per cent. Even with fresh spores 

 germination could not always be induced in distilled water. 



EFFECT OF TEMPERATURE UPON THE GERMINATION OF THE BASIDIOSPOBES. 



In these studies both percentage and rapidity of germination have 

 been noted. It is interesting to know the rate at which these spores 

 germinate, but of the two criteria percentage would be likely to give 

 the best indication of the effect of various environmental conditions. 

 From the point of view of infection of structural timbers, if a large 

 percentage of spores will germinate over a wide range of temperatures 

 it makes little difference whether it takes three or four days for 

 them to germinate at 10° C. (49° F.) or only 16 hours at the optimum 

 rate of germination. The chances for infection, however, are some- 

 what greater at the optimum temperatures, because of the somewhat 

 larger number of spores capable of germinating. The percentages 

 given herewith have no absolute value, either for the individual 

 species or for purposes of comparison between species. It is possible 

 that spores collected from different fruit bodies of the same species 

 of different degrees of maturity, from different climatic conditions, 

 and under different conditions of casting might give varying per- 

 centage values. It is certain that age is a factor. Hence, that one 

 species should give 75 per cent germination at the optimum tempera- 

 ture and another only 40 per cent does not mean that the spores of 

 the one are inherently more vigorous than those of the other. In 

 the data presented germination is taken to consist in a germ tube at 

 least as long as the swollen spore. The data for the effect of tem- 

 perature upon germination are given in Table 1 and in figure 1. 



For Lenzites sepiaria with certain variations tests showed that 

 between 12° and 40° G. (53° and 104° F.) there was little difference 

 as to the effect of temperature upon the percentage of germination if 

 the time element was disregarded. The optimum for rate of germina- 

 tion was between 32° and 36° C. (89° and 97° F.), an optimum 

 somewhat lower than that obtained by Falck. At 40° C. (104° F.) 

 the results varied with the age of the spores. Those a few months 



