12 - THE CHICAGO ACADEMY OF SCIENCES 



ochraceous to dark brown, and purple to dead black. Many are 

 spherical, others ellipsoid, oblong, cylindrical, or fusiform, while 

 not a few are obovate or pyriform. their surface may be smooth, 

 granular or echinulate. Typically four are produced from the 

 apex of each spicule or basidium. 



The sporophore with its hymenium forms the conspicuous 

 part of the fungus, and it is this portion that is chiefly considered 

 in the classification of species. Detailed mention of its forms and 

 characters will be found in the generic keys on succeeding pages. 

 It may be noted that the duration of life of the sporophore 

 varies immensely in different species. Some Coprini spring up 

 literally in a night and disappear with the morning sun, while 

 other species may continue to grow for many years. Fomes 

 igniarius is said to attain the age of eighty years. (Atkinson, Am. 

 Fungi, p. 194.) 



Many problems in the life history of these plants are yet to be 

 worked out. All of our species are considered saprophytes, yet 

 it is known that the mycelia of certain species produce a soluble 

 ferment which extends into and affects injuriously the living tis- 

 sues of plants, probably to the advantage of the fungus. Still 

 other species appear to have established such symbiotic relations 

 with growing trees and shrubs that fungus and host are enabledto 

 thrive, each at the expense of the other, without detriment to either. 



The duration of life of the mycelium of many species is un- 

 certain, and the conditions under which fructification may occur 

 are imperfectly understood. Some species of Lentinus and Lenz- 

 ites may persist for years in railroad ties or bridge timbers, finally 

 causing a total disintegration of the wood without the appearance 

 of a sporophore at any stage of growth of the fungus. 



The coloration of species, their chemical composition, particu- 

 larly with respect to toxic properties that may appear at certain 

 stages of growth while absent at others, and in varying intensity 

 in plants grown in different soils or localities, are mat mcern- 



ing which too little is known. 



The dissemination of species is another matter little studied. 

 Many kinds are erratic in their appearance. They may be 

 abundant one season, disappear altogether for one or more years 

 and then reappear in large numbers, while other species apparently 

 similar in their climatic requirements have occurred regularly 

 each season. 



Modern commerce brings to us the wood and other tree prod- 

 ucts of every part of the globe. With these are undoubtedly 

 imported the spores and mycelia of saprophytic fungi, both in 

 the tissues of the wood and in or upon tin- bodies of burrowing 

 larvae. So limited is our knowledge of the geographical distri- 

 bution of our native fungi, that it is possible for species thus 

 introduced to increase and thrive for years without being recog- 

 nized as exotic. 



The structural and physiological modifications that must ac- 

 company a change of environment do not appear to have received 



