DECAY 



181 



more prominent way than in any other group of plants, though 

 the general relations also hold true for all the higher fungi. 

 Thus among the bacteria certain forms have been known to 

 survive a temperature of - 10 C., or even - - 100 C. when the 

 cold is applied for a short time only. On the other hand, Bacil- 

 lus thermophilus thrives vigorously at a temperature of 70 C., 

 while the spores of the common hay bacillus (B. subtilis), which 

 are destroyed when heated in their nutrient solutions to temper- 

 atures exceeding 100 C., are nevertheless capable of resisting 

 upwards of 120 C. of dry heat. From these and similar well- 

 known examples it may be concluded that the specific effect of 

 varying temperatures is due to the amount of water present in 

 the albuminoid protoplasm, --a conclusion in accord with the 

 reduction of water which is known to take place in a cell when 

 it passes from the active vegetative to the resting state, in which 

 form it manifests its highest powers of resistance to extreme 

 conditions of temperature. This principle finds its further illus- 

 tration in the fact that the vegetative cells of fungi, which con- 

 tain a maximum of water and are adjusted to certain conditions 

 of temperature, may be readily killed by dryness, for which pur- 

 pose desiccation at the ordinary temperature is often sufficient. 

 Broadly speaking, the bacteria cannot survive a temperature 

 exceeding 50 to 60 C., and in this connection a statement of 

 the three critical points in temperature for a few well-known 

 forms, as given by Warming, may be instructive : 



Turning our attention to the fungi, which are more immedi- 

 ately concerned in the destruction of timber, we find that with 

 the exception of certain specialized forms the three critical points 

 in temperature may be stated as minimum, i to 2 C. ; optimum, 



