The Biology of Polyporus Pargamenus Fries 17 
effectually. As a result of the increasing favor with which 
this phase of plant pathology has met, an extensive literature 
on the subject has been assembled gradually. Despite our 
rapid progress in certain fields, we as yet know but little 
concerning the life histories of our wood-destroying fungi, 
supplemented by detailed and accurate information as to the 
way in which they bring about decay in wood, together with 
the chemistry involved in the process of decay. The pre- 
vention of the destruction of wood by any particular fungus 
presupposes a definite knowledge of its biologic and physio- 
logic relations. Since we still are lacking this knowledge 
for the species here selected for investigation, detailed studies 
have been undertaken, placing foremost the interests of 
dendropathology and technical science. 
Geographic Distribution and Host Woods of Polyporus 
Pargamenus. 
Polyporus pargamenus is of wide geographic distribution, 
occurring on most any of the dicotyledonous, although rarely 
the coniferous, trees in many parts of the world. In the 
United States this fungus is of especially common occur- 
rence in the great deciduous forests east of the Mississippi 
River, but of only scattered occurrence throughout the states 
west of the Mississippi River. Even here its occurrence in 
most all the states would lead one to expect that it will be 
reported eventually from every state, since Populus tremu- 
loides Michx., which occurs in all of the western states, 
serves as a host to bridge the prairie states, Polyporus par- 
gamenus having been collected on this species from points 
as far west as North Dakota, Colorado, and New Mexico. 
Collections of this fungus have been recorded from all states 
of the United States but Nebraska, Wyoming, Nevada, Cali- 
fornia, and Arizona. I*rom the United States Polyporus par- 
gemenus extends northward into southern Canada, authentic 
collections being recorded from British Columbia, Ontario, 
Quebec, Nova Scotia, and Newfoundland. The fungus lke- 
wise extends southward through Mexico and Central America. . 
