39 



very loosely interwoven hypha3 grows out at right angles to the bark. 

 From the lower side of this band some hyphii? split off and grow down- 

 ward, adhering closely to the surface of the bark. Other hyphje also 

 turn down, growing faster at several points than at others, thus giving 

 rise to small pits, which form the beginning of the pores. The pits are 

 very variable in size. When the}' are still scarcely recognizalde the 

 hymen ial laver begins to form in them, as evinced by the black cystidia 

 which can be seen projecting from the lower surface of the band first 

 mentioned even before any sign of a ridge is evident to indicate where 

 the next pore is to be. Growth in these directions goes on rapidly. 

 The hyph^e of the original band grow on horizontally, forming a 

 rounded edge of loose hyphte, which give the hairy appearance to the 

 margin. At intervals, where the growth of the sporophore ceases, 

 some of these loose hyphiv stop growing, and when growth is resumed 

 are left, forming a brush-like projection on the upper surface. These 

 hyphae give the concentric appearance noted above for the Spruce. 

 The hypha^ on the lower side of the liand grow^ downward to form the 

 pores, and those adhering to the bark grow in the same direction, thus 

 increasing the thickness of the pileus in that direction. A large num- 

 ber of small cushions usually start together on the bark, many of which 

 join as their edges approach one another, forming a series of more or 

 less imbricated sporophores (see PL XII, lig. 1). On horizontal sur- 

 faces the pileated form is lost, and sheets nuich like those found in 

 the Spruce are formed. The pores in all the specimens on the Fir 

 are more irregular than those found on the Spruce, but in all other 

 important characters they are identical. 



On the AVhite Pine the pileus is sessile and occurs at old knot holes. 



On the Tamarack both brackets and sheets are formed. The largest 

 bracket forms found grew on the Tamarack; they often grow singly, 

 and then again together, one above the other. One individual meas- 

 ured tt inches (10 "'") in width laterally, 2.8 inches (7 '''') from front to 

 back, and 2 inches (5 *"") in thickness at the back along the bark (PI. 

 XII, tig. 2). The pores in the Tamarack specimens are exceedingl}^ 

 regular, far more so than in those of any of the other sporophores. 



The sporophores of TrameteH jyini forma iibietis grow both on living 

 and fallen trees. They were found on trees which had been cut 

 dowMi four years before, and new ones were constantly appearing. 

 It is this faculty of fruiting on dead trees that umst enable this fungus 

 to spi'ead through a forest in a very short time, and accounts for 

 the fact that it does so. After a Spruce has reached a certain age 

 the chances that it Avill become affected Avith this parasite are, in 

 the Maine woods, the ver}' greatest. Older trees, i. e.. Spruces which 

 have reached a diameter of 10 to 12 inches, are more often subject to 

 attack than younger ones. The fungus enters through any wound, 

 and apparently spreads rapidly. There is no evidence at present to 



