54 



PLATE VIII. 



Fig. 1. Piece (X|) of wood of tamarack or larcli { Larlx I'tricina), showing early 

 stage of the decay caused by TrameUss p'nu (Brut.) Fr. forma ahlelis Karst. Note 

 how the annual rings separate at one end. 



Fig. 2. Piece (X|) of tamarack wood, showing an advanced stage of the same 

 decay. The piece is composed of very little sound wood; the larger portion is 



cellulose. 



PLATE IX. 



Fig. 1. Radial view of two spruce tracheids, showing the manner in which cracks 

 appear in the walls when such wood is destroyed by Polyporus sclmehutza Fr. 



Fig. 2. A pore from the sporophore of Trametes pin'i ( Brot. ) Fr. forma aUetU Karst., 

 growing on Ahii's Ixdmmm, showing numerous cystidia projecting from the hymenial 

 layer. 



Fig. 3. Enlarged view^ of a portion of the hymenial layer shown in fig. 2, showing 

 cystidia with thick walls and several basidia with spores. 



Fig. 4. View (Xj) of the lower surface (jf an old pileus of Polyporus pinicola 

 (Swartz) Fr., of which a portion has died. This is shaded dark. Hyph?e from the 

 living parts are forming a new layer, which is slowly covering the dead parts. The 

 pores are indi(;ated by the dots. 



FiG. 5. Young sporoplKjre (natural size) of Polt/porna pinicola, cut in the middle 

 to show arrangement of pores and top. 



FiG. 6. Resupinate form (natural size) of pileus of the same fungus. 



Fig. 7. Older pileus (natural size) of the same fungus, sectioned through the 

 middle. 



Fig. 8. Diagrammatic representation of a section through the pores of Polyporus 

 pinicola. They are continuous from year to year. A firmer layer of hyphte, 

 incrusted with crystals of oxalate of lime, forms a line of demarcation between 

 successive growth increments. 



Fig. 9. Cross section of wood elements from summer wood of Spruce {Picea ruhnia 

 Sarg. ) attacked by Tratiicl>'s jiiiii iormsi ahidis, showing how the fibers are grachially 

 changed until only cellulo.se is left; " w," unchange<l w(jod libers; "b," the outermost 

 lamelU* (unshaded) now consist only of cellulose; "c," more advanced stage; "e," 

 the middle lamella is being converted into cellulose, and is finally absorbed, leaving 

 only portions " p" free among the white cellulose libers. 



Fui. 10. Radial view of tracheids from wood of Spruce {Picea ranademia (Mill.) 

 B. S. P.) attacked by Trametes pirn forma abielis, in tlie region of a hole fringed by a 

 black line. (See PI. VI, fig. 2.) The tracheids are filled successively with hyphse, 

 which are incrusted with a brown material so as to completely plug the tracheitl. 



Fig. 11. Tracheid from wood of Spruce {Picea canademift (Mill.) B. S. P.) during 

 early stage of attack by Trametes pini forma abietis, showing hyphse. 



Fig. 12. HymeniaWayer oi Polyporus pinicola (Swartz) Fr. 



Fig. 13. Radial view of white area from wood of Balsam fir (Abies bahamea (L. ) 

 Mill.) attacked by Trametex pini (Brot) Fr. forma abietis Karst., showing how the 

 hyphfe gradually recede from a center, forming plugs in every wood element. The 

 pings are colored almost black 1)y a brown product of decomposition. 



PLATE X. 



Fig. 1. Cross section of Spruce wood partially destroyed by mycelium of Polyporus 

 pinicola. Large cavities and breaks which are filled with fine hyphse are being 

 formed in the wood. The summer wood is indicated l)y the parallel shading, the 

 hyphic )jy dots; "c," a small fi.ssure enlarged in text figure 2. The lines at the 

 left =0.5""". 



