55 



Fk;. 2. Croi^s section <>f a jiit-cc of Si»rncc' wood, .-^lajwiiiif t'arly stajre of destniction 

 by Tnuiietex pini forma (ihlctis. Parallel lines of holes filled with cellnlose fil)ers, here 

 indicated by dots, appear in the wood. The l^lack lines bounding the cavities simply 

 itidicate the limit of change of cellulose, ior in reality there is no such sharp line of 

 demarcation. The short line at the right equals about /- of an inch (1'""'). 



Fic. 3. Later stage of the same form of decay. The wood is now simply a network 

 of narrow wood lamella) separating larger and smaller holes. In these lamelhe black 

 lines are shown, which represent plugs of brown hyph^e incrusted with decomposition 

 l)roducts. (See PL IX, figs. 10 and 13. ) Cellulose fibers and mycelium fill some of the 

 cavities. The short line at the base equals about .j^^ of an inch (!"""). 



Fk!. 4. Longisection of wood (Spruce), showing effects of destruction l)y liyphjc of 

 Poliiponis j)in in/la. 



Fk;. 5. Cross section of several wood cells, showing clianges which take })lace in 

 wo(xl such as shown in fig. 4. 



PLATE XL 



Fk;. ]. Tangential view of Spruce wood destroyed ])y mycelium of Polyjjorux sid- 

 fnirii.s (Bull) Fr. : "a" wood elements which have been curved, bringing two med- 

 ullary rays in^o line; " e" part where a break occurred, uniting two medullary rays. 



Fig. 2. Kadial view of wood in last stage of decay, induced by mycelium of Pobj- 

 porm siihacidns Pk. The straight black lines represent one or more wood elements 

 held in place by the hyphjc which are wound all around them. Remnants of medul- 

 lary rays are to bo seen here and there. 



Fk;. 3. Several cells from such a piece as is shown in fig. 2 (also PI. XIV, fig. 3). 

 Xornial wood cells of the spring wood are shown at the left, and going toward the 

 right various stages in the solution of the cell walls. 



Fk;. 4. Tangential view of a piece of Spruce wood destroyed by mycelium of Pobj- 

 jjoras snlfureus, showing characteristic breaks in the wood, formed by the uniting of 

 many medullary rays by cross breaks. (See fig. 1 of this plate.) The short line at 

 the left is equal to 1"™. 



PLATE XII. 



Various forms of sporophores of Trcuaetcs pini forma ahietis. 



Fk;. 1. On Balsam Fir. 



Fig. 2. On Tamarack. 



Fig. 3. On horizontal Ijranch of Sjjruce. 



Fig. 4. On bark of trunk of Spruce. 



Fig. 5. At base of dead branch of Spruce. 



Fig. 6. Semipileate form on Spruce. 



Fig. 7. At base of dead branch of Spruce. 



PLATE XIII. 



Radial view of a block of White Spruce {Picea (■(tnadcitsi.'^ (Mill.) B. S. P.) partly 

 destroyed by mycelium of Pohjporun snlfureus. The darker spots at one side show 

 where the wood turns brown and ultimately cracks. The manner in which the 

 annual rings separate is indicated near the top of the figure. 



PLATE XIV. 



Fk;. 1. Radial view of White Spruce {Picea canadensis), showing early stage of 

 destruction by Pobjporus mhacidii>< Pk. 



Fk;. 2. Radial view of White Spruce log showing destruction of wo(jd V)y mycelium 

 of Poll/poms subacidus Pk. The white lines show where the wood has been so 



