36 OUTLINES or lUllTISII FUNGOLOGY. 



pearancc, and do not cease till wc reach an altitude of 18,000 

 feet. 



In respect of genera, they are in general diffused almost 

 indiscriminately over the surface of the globe. A few genera 

 only are peculiar to warm climates, and some of these have 

 their representatives on either side of the basin of the Medi- 

 terranean. The same species occur sometimes at great dis- 

 tances from each other, being confined to small districts in 

 each locality. Java, the Sikkim Himalayas, New Zealand, 

 and South Carolina, produce a curious plant,* allied to Gcaster, 

 which occurs on decayed laurels, without any intermediate 

 stations, and other instances might be brought forward. The 

 species which occur in different tropical countries often differ 

 widely, especially the PoJypor'i, but it is certain that there are 

 hundreds of undescribcd species to reward future researches, 

 and till the genus has been more closely studied, it is difficult 

 as yet to come to any accurate conclusions. 



As regards cosmopolite species, it is curious that the com- 

 mon INIushroom is one of the most universally diffused, but 

 it may be doubted whether this has not accompanied the in- 

 troduction of the horse, consequent on the dispersion of the 

 human race. 



But little has at present been made public respecting the 

 distribution of species in Europe. Fries is, however, collect- 

 ing materials for the solution of this difficult question. The 

 great evil is, that so few persons have made such a critical 

 study of the more important species which retain their cha- 

 racters but imperfectly when dried, that if is not always 

 possible to give implicit credit to lists of species which may 

 be published in local Floras. Indeed^ some notion of the 

 difficulty may be found from the frequent alterations of sy- 



* Tricliosptjtale paradoxa. 



