39 



veiy loosely interwoven hypha? grows out at right angles to the bark. 

 From the loAver side of this band some hyph* split oil' and grow down- 

 ward, adhering closely to the surface of the bark. Other hyph^ 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 they are still scarcely recognizable the 

 hymenial layer 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 hyphffi of the original band grow on horizontally, forming a 

 rounded edge of loose hyph^e, which give the hairy appearance to the 

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

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

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

 hyphse give the concentric appearance noted above for the Spruce. 

 The hypha? on the lower side of the band 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 thel)ark, many of which 

 join as their edg«^s approach one another, forming a series of more or 

 less imbi-icated sporophores (see PI. XII, fig. 1). On horizontal sur- 

 faces the plicated form is lost, and sheets much 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 White 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 4 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, fig. 2). The pores in the Tamarack specimens are exceedingly 

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



The sporophores of Tixmietes pini forma ahietis grow both on living 

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

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

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

 to spiead 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 will become affected with this parasite are, in 

 the Maine woods, the very 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 ai)parently spreads rapidly. There is no ('vidcMicc at ])rcsent to 



