236 



WOOD AND FOREST. 



Of the shelf fungi, which project like brackets from the stems of 

 trees, and have their pores on their under surfaces, one of the com- 

 monest in many localities is the yellow cheese-like Polyporus sulphu- 

 reus, Fig. 83. This is found on oak, poplar, willow, larch, and other 

 standing timber. 



Its spawnlike threads spread from any exposed portion of cambium into 

 the pith-rays and between the annual rings, forming thick layers of yellow- 

 ish-white felt, and penetrating the vessels of the wood, which thereupon 

 becomes a deep brown color and decays. 



Of the umbrella-shaped gill-bearing fungi, a yellow toadstool, 

 called the honey mushroom (Agaricus melleus], is a good example, 

 Fig. 84. 



This fungus, of common occurrence in 

 the United States as well as in Europe, is 

 exceedingly destructive to coniferous trees, 

 the white pine in particular suffering greatly 

 from its attacks. It also fastens upon vari- 

 ous deciduous species as a parasite, attack- 

 ing living trees of all ages, but living as well 

 upon dead roots and stumps and on wood that 

 has been cut and worked up, occurring fre- 

 quently on bridges, railroad ties, and the 

 like, and causing prompt decay wherever it 

 has effected an entrance. The most conspicu- 

 ous part of the fungus is found frequently in 

 the summer and fall on the diseased parts 

 of the tree or umber infested by it. It is 

 one of the common toadstools, this particular 

 species being recognized by its yellowish color, 

 gills extending downward upon the stem, 

 which is encircled a little lower down by a 

 ring, and by its habit of growing in tufts or 

 little clumps of several or many individuals 

 together. It is also particularly distinguished 

 by the formation of slender, dark-colored strings, consisting of compact 

 mycelium, from which the fruiting parts just described arise. These hard 

 root-like strings (called rhizomorphs) extend along just beneath the sur- 

 face of the ground, often a distance of several feet, and penetrate the roots 

 of sound trees. By carefully removing the bark from a root thus invaded 

 the fungus is seen in the form of a dense, nearly white, mass of mycelium, 

 which, as the parts around decay, gradually produces again the rhizomorphs 

 already described. These rhizomorphs are a characteristic part of the 

 fungus. Occurring both in the decayed wood from which they spread to 

 the adjacent parts, and extending in the soil from root to root, they constitute 

 a most effective agency in the extension of the disease. 



Fig-. 83. "Shelf" Fungus on 

 Pine. a. Sound wood;. Kesin- 

 ous"ligtit" wo d; c. Partly de- 

 cayed wood or punk; d. Leaver 

 of living spore tubes * Old 

 filled-up spore tubes; f. Flut- 

 ed upper surface of the fruit- 

 ing- body of the fungus, which 

 g-ets its food thru a great 

 number of fine threads (the 

 mycelium), its vegetative tis- 

 sue penetrating- the wood and 

 causing its decay. [After 

 Hartig.} 



