30 



in older ones. It is composed of looseh' interwoven hyphse, which 

 form a continuation of the main hyphal strands which compose the 

 body of the pileus. The hyphse of the latter start from a central 

 point on the bark and radiate out in several directions (PL IX, fig. 7), 

 forming- a mesh which at first is very loose. The hyphai are almost 

 colorless and have a decided lumen. As they grow older their walls 

 become brown and very thick, so that the lumen is reduced to a very, 

 small one. The peripheral growth of the hyphaj takes place in such 

 a way as to form well-defined la^^ers. For .several years these laj^ers 

 are added one outside of the other. The lowermost portion of each 

 laj'er is usually less dense than the outer portion, and after the hyphse 

 turn brown large masses of crystals of calcium oxalate are deposited 

 in the meshes of the outer portion. The alternation of layers of less 

 density with those of greater densit}" makes a differentiation of laj'ers 

 possible. The laj^ers vary considerably in width (PI. IX, figs. 5-7), 

 and it is suggested that this is probably due to varying conditions; 

 probably the amount of food supplied and the amount of available 

 moisture exert a marked influence. The pileus grows in width and 

 length by the direct elongation of the hyphie of the last layer. After 

 several 3'ears' growth the hypha- on the under side of the developing 

 shelf grow down in a vertical direction and give rise to the pores. 



The pores. are ver}^ long and are continuous from year to year. 

 After a time the}^ become plugged at the l)ottom by hj-ph^e which 

 grow into them from all sides. Different sporophores differ in this 

 respect. With some the pores are open through eight or ten of the 

 recent layers; in others the growth of hyphai is so vigorous that the 

 pores are closed almost as rapidly as they are formed. The h^^menium 

 arises on the surfaces of the pores from hyphte of the trama which 

 turn at right angles to the general direction of the tramal hyphse. 

 The latter have very thick walls (PL IX, fig. 12) and extend longitudi- 

 nally, forming a very loose network. The tips of those hypha? which 

 form the hymenial laver are thin walled. The hymenial layer itself 

 is composed of hyphre of almost equal width. The layer is a very 

 narrow one. Cystidia are practically alisent. The basidia barely 

 rise above the general surface and do not differ materially in form 

 from the paraphyses. The four spores are colorless. Amid the 

 tramal and hymenial hyphfe accumulations of calcium oxalate crystals, 

 colored red-brown, occur in great numbers, likewise large quantities 

 of an oil readil}' soluble in ether and becoming solid at about 59" F. 

 (15'^ C). The growth of the hymenial la^^er is very irregular. At 

 one and the same time pores ma}' be forming on one side, while at the 

 opposite side the old pores are completely plugged. The h3'menium 

 renews itself at frequent intervals. The vitality of its hyphsB is very 

 great, for it is not at all rare that insects eat away a considerable por- 

 tion of the lower side of the pileus. These parts die and turn brown. 



