Geographical Dish^ibidion. 43 



sistent in following their hosts. The potato was intro- 

 duced into Europe by the Spaniards before the middle 

 of the sixteenth century, and its fungus parasite, 

 Fliijto'ptliora infestans, found on the wild potato in 

 Chili and Peru, followed, or at all events first 

 attracted attention by its sudden onslaught on potato 

 crops two hundred years later. Saprophytic fungi 

 enjoy a greater amount of freedom in this respect, yet 

 the great majority obtain their food from decaying 

 vegetable matter, and here too, in most instances a 

 certain amount of selection is exercised, as it is well 

 known that we have fungi characteristic of fir-woods, 

 beech-woods, open pastures, &c. The general dis- 

 tribution of the large fleshy and woody species is best 

 known, and the soft, annual, gill-bearing species, 

 included in the genus Agaricus in the wider sense, are 

 especially characteristic of the colder parts of the 

 north temperate zone, but species are scattered 

 throughout the tropics, more especially at great 

 elevations. The more persistent and leathery or 

 woody gill-bearing species which connect the 

 Agariciness with the PolyporesBj as Lenzites and 

 Lentinus, are cosmopolitan, but are far more numerous 

 and more highly developed in the tropics. In the 

 Polyporece. the genus Boletus is characteristic of cold 

 zones, Polyporus and Trametes extend from the colder 

 portions of the north temperate zone to the tropics, 

 but both genera are by far most numerous in the 

 latter region, while the genera Favolus, Hexagona, 

 and Laschia are very common in the tropics and 

 exceedingly rare in temperate regions. The following 

 summary the of distribution of the Eymenomycetes 



