54 



PLATE VIII. 



Fig. 1. Piece (Xf) of wood of tamarack or larch {Larix Jdrichm), showing early 

 stage of the decay caused by Trametes pini (Brot. ) Fr. forma ahletis Karst. Note 

 how the annual rings separate at one end. 



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



decay. The piece is composed of very little sound wood; the larger jjortion 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 schweinitzii Fr. 



Fig. 2. A pore from the sporophore of Trametes pini (Brot. ) Fr. forma abiciis Karst., 

 growing on Abies balsamea, 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 (Xi) of the lower surface of an old pileus of Polyporus pinicola 

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

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

 pores are indicated by the dots. 



Fig. 5. Young sporophore (natural size) of Polyp)orns 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 hyphse, 

 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 rubeiis 

 Sarg. ) attacked by Trametes pini forn:ia abietis, showing how the fibers are gradually 

 changed until only cellulose is left; "w," unchanged wood fibers; "b," the outermost 

 lamellie (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 fibers. 



Fig. 10. Radial view of tracheids from wood of Spruce {Picea canadensis (Mill.) 

 B. S. P. ) attacked by Trametes pini forma abietis, in the region of a hole fringed by a 

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

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



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

 early stage of attack by Trametes jnnl forma abietis, showing hyphas. 



Fig. 12. Hymenial \siyer oi Polyporus pinicola (Swartz) Fr. 



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

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

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

 plugs are colored almost black by a brown product of decomposition. 



PLATE X. 



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

 pinicola. Large cavities and l)reaks which are filled v/ith fine hyi)hjTe are being 

 formed in the wood. The summer wood is indicated by the parallel sliadlng, the 

 hy])ha' by dots; "c," a small fissure enlarged in text ligure 2. The lines at the 

 left =0.5""". 



