GEOGRAPHICAL DISTKI BUTION OF FUNGI. 37 



iionyms which appear in the works even of the best Fungo- 

 logists. Much remains also to be done in the south of Eu- 

 rope, notwithstaucliug the labours of such trustworthy autlio- 

 rities as Vittadini, and till the Southern Fungi are worked out 

 in the same spirit and with the same accuracy with which 

 he has attacked a portion of the Fungi of Italy, it will be 

 impossible to ascertain correctly the limits of species. 



It is requisite, however, not only to study their limits in 

 latitude, but the geological limits also. These will probably 

 prove far more striking. The predominance of Truffles in 

 limestone formations above other strata is a well-known fact, 

 and there is little doubt that a comparison of lists belonging 

 to different formations would give equally striking results in 

 other groups. The subject is well worth attention, and will 

 be found highly interesting to those who have facilities of 

 visiting different districts for comparison. It must be re- 

 membered, in considering this subject, that species cannot 

 become permanent inhabitants of any district if extremes 

 exist destructive to their spawn. Excessive drought, or mois- 

 ture, extreme heat or cold at certain times of the year, may 

 prevent the establishment of a species, especially where that 

 species is a long time before it sends up perfect fruit from 

 its spawn. It is probable that few ever make their appear- 

 ance which are not able to exist permanently. The Vine Mil- 

 dew and Potato Mould are at present examples in favour of 

 this notion, but it is to be hoped that, under some peculiar 

 concurrence of circumstances fatal to their growth, they also 

 may at length entirely disappear. 



But little can be said of the occurrence of Fungi in earlier 

 periods of the earth, before the introduction of man into the 

 universe. No certain traces of Fungi are to be met with till 

 very recent periods, though a few anomalous productions have 



