236 



WOOD AND FOREST. 



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

 trees, and liave their jjores on their under surfaces, one of the com- 

 monest in man}' localities is the j'ellow cheese-like Polyporus sulphu- 

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

 standing timber. 



Its spawnlike tlireads spread from any exposed portion of cambium into 

 the pith-rays and between the annual rings, forming thiclc 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 honej' mushroom {Agaricus mellcus), 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 ]>articular suH'ering 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 

 I-] on ilcad routs and stumps and on wood that 

 li:'S Ijcen cut and worked up, occurring fre- 

 quently on bridges, railroad ties, and the 

 like, and causing prompt decay vherevcr it 

 has cfl'ectcd an entrance. The most conspicu- 

 ous part of the fungus is found frequently in 

 the sunuuer and fall cjn the diseased parts 

 of the tree or limber infested by it. It is 

 one of the common toadstools, this particular 

 species being recognized by its yellowish color, 

 gills extending downward u]win the stem, 

 which is encircled a little lower do^VTl by a 

 ring, and by its habit of growing in tufts or 

 little clumps of several or numy individuals 

 togetlier. It is also partioilarly distinguished 

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

 mycelium, from which the fruitiiru' parts just deseribed arise. These hard 

 root-like strings (callcil rhizomorjihs) extend alimg 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 fungais is seen in the fornr 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 aL'eney in the extension of the disease. * » * 



Fig-. S3. "Shelf" l'"mii,>-us on 

 Pine. it. Sound wood;/'. Kesln- 

 ous^lig-lil" wo d;t. Partly de- 

 cayed wood or punk; J. Laver 

 of livin}/ spore lube-; t'. Old 

 filled-up spore tubes; f. Klul- 

 ed upper surface of the fruit- 

 ing- body of the fungus, which 

 g-ets ils food thru a g-reat 

 number of fine threads [the 

 mycelium), iis vegetative tis- 

 sue penetrating the wood and 

 causing its decaj-. [After 

 Harlig'.\ 



