FUNGI 315 



state. This time extends in numerous instances to one or two years, and, 

 in the case of spores of Ustilagineae especially, to longer periods. The 

 spores of Tilletia caries (Tul.) germinated after eight and a half years, and 

 those of other species after shorter intervals varymg from seven and a half 

 downwards. Resting-spores^ or those of the second category, generally un- 

 dergo more or less definite periods of rest corresponding to periods of vege- 

 tation. "While germination cannot be procured before the lapse of this 

 time, they frequently exhibit inability to survive the occasion presumed 

 to be favourable. Such are hibernating spores like the teleutospores of 

 Uredine^, and the oosperms of Peronospore^e. Resting-cells belonging 

 to saprophytes again, e.g. the zygosperms of 3tIucorini, while they undergo 

 a necessary period of rest of varying duration, yet display no partiality 

 for seasons of the year, and this also is intelligible in view of their mode 

 of life. 



The power of resistance of spores to external agencies operating 

 against their vitality is in many instances very great. The spores and 

 zygosperms of several Mucorini withstand mechanical injury and re- 

 pair slight wounds while preserving the power of germination. Short- 

 lived spores and those of aquatic fungi do not bear desiccation ; but 

 a great number of spores retain the power of germinating, as has been 

 stated, for considerable periods in an air-dry state. Spores adapted for 

 hibernation in temperate climates, and, it may be assumed, long-lived 

 spores, withstand very low degrees of temperature, ranging below zero 

 C. ; while such long-lived spores, on the other hand, are very^ sensitive 

 to high temperatures. The capacity for germination after exposure to 

 high temperatures is maintained or not within certain degrees, according 

 to the dryness or humidity of the environment. Thus it has been 

 shown that while no spores are known to withstand a temperature of 

 loo"^ C. in water or w^atery vapour, and many perish under these circum- 

 stances at much lower temperatures, the same spores can endure a 

 considerably higher temperature in a dry state. Dry spores of some 

 fungi have been found to withstand temperatures up to 120'' C. 

 and beyond, but it is probable that 130° C. marks the death-point of 

 all. Others, again, perish at degrees considerably below 100^ C. It 

 must, of course, l^e borne in mind that the duration of the exposure is 

 an important factor in such experiments, and that spores which support 

 a high temperature for a few minutes or an hour are killed by longer 

 exposure. It is probable that much individual variation exists in 

 regard to this matter and to the duration of life under ordinary circum- 

 stances, and that in this lies the explanation of conflicting results ob- 

 tained by different experimenters. 



There is not much known as to the maximum, minimum, and 



