40 



show how rapidly it spreads, nor whether the (•haracteristic form of 

 decay which it induces continues in wood after it has been cut from 

 a tree or not. The present view seems to indicate that it does not 

 grow after the death of the tree. 



HYIVIENIUM. 



Hartig ^ has given a very full description and numerous drawings 

 of the hymenial layer of this fungus, and his observations can simply 

 be confirmed. The basidia arise as slender hyphae, which gradually 

 become much smaller at the apex and form four slender, rather long 

 sterigmata, bearing the spores. These are colorless at first, but turn 

 brown later on, and not infrequentl}" contain an oil globule in the 

 center. The most striking elements of the hvmenial laver are the 

 C3"stidia, called hairs by Hartig. They arise from internal hyphfe, 

 which approach the hymenial laj^er at an angle. Pushing between the 

 basidia and paraphyses one finds these large, pointed, brown, spine- 

 like bodies, which project for a considerable distance into the pore 

 canal (PL IX, figs. 2 and 3). They are thick walled and persist for a 

 long time after the disappearance of the basidia and spores. 



As the pores grow older they are filled with a network of hyphse 

 which grow out from the liody of the sporophore, growing over the 

 hymenial layer and completely plugging the hole. The exact period 

 when this takes place was not determined. 



POLYPORUS SULFUREUS ( Bull. ) Fr. 

 OCCURRENCE. 



This fungus, although more frequently found on the hardwood trees, 

 occurs now and then on living Spruces and brings about a brown rot 

 of the wood of trunk and branches. The trees found were attacked 

 after the trunks were 9 inches (23*^™.) in diameter. Entrance is efi'ected 

 through wounds and broken branches, much in the same wa}" as the 

 other parasitic fungi which enter above the ground. The mj^celium 

 spreads through the trunk of an afi'ected tree, growing up and down, 

 and reaching the highest branches in one direction and the roots in 

 the other. No evidence of a diseased condition is usually visible on 

 the outside, except such as noted for the other diseases. 



STRUCTURE OF DISEASED WOOD. 



Diseased wood is red-brown in color and can readilv be distino-uished 

 from wood changed by the other fungi described by the fact that it 

 breaks into slabs or flat pieces, which correspond each to an annual 

 ring of wood (PI. XIII). The brown rotted wood is hard, verj^ brittle, 



1 Hartig, R. Wichtige Krankheiten der WaldbiiunK'. 50. pi S. 1874. 



