53 



EXPLANATION OF PLATES. 



platp: I. 



Fig. 1'. Sporophores of Polyporiij^ ^clavemitzii Fr. 



Fui. 2. A piece of the bark of Red Spruce with sporophores of Polyporun volvntun 

 Peck growing from holes forinetl by a boring beetle, a species of Deiidroclonua. 



PLATE II. 



Cioss section (X|) of the trunk of a living young Balsam Fir [Abies halsamea (L. ) 

 Mill.) at a point 4 feet (1.2 meter) from the ground. Decay, caused by Polyporus 

 sclnreluitzii Fr., has shrunk the wood, jjroducing a number of cracks and giving it a 

 rough appearance. It is so nonresistant that the saw tore the fibers instead of cut- 

 ting them. The large crack at the top, extending through the sapwood, was formed 

 when the tree was cut down. A small sporophore of the fungus grew at the base of 

 this tree. 



PLATE III. 



Radial view (X j) of a log of White Spruce (Picea canndnisi.'i (L. ) B. S. P.) , showing 

 an early stage of decay induced by the mycelium of Polyporus pinicola (Swartz) Fr. 

 The fine parallel lines indicate the annual rings of wood. Here and there white spots 

 with darker centers are seen; likewise long white lines parallel to the course of the 

 wood fibers, and others near tlie center of the figure, which extend in an irregular 

 manner across the direction of the libers. 



PLATE IV. 



Radial view (Xz) of a log of White Spruce {Picea canadensis B. S. P.) , showing an 

 advanced stage of decay induced by mycelium of Poly poms pinicola (Swartz) Fr. 

 The wood has cracked throughout. The white masses are sheets of mycelium. At 

 the right of the figure two sporophores are shown — one just beginning to develop, 

 the other about 1 year old. The sapwood has been partially destroyed by boring 

 larvse, whose tunnels are filled with sawdust. 



PLATE V. 



Three sporophores (Xj) of Polyporus pinicola (Swartz) Fr. The uppermost one 

 is a young one. The one on the right is growing on a stump, and its lower surface is 

 much eaten by insects. The one on the left is a very old sporophore, in which the 

 ridged ujtper surface is very marked. 



PLATE VI. 



Fig. 1. Radial view of a piece of wood (natural size) of the Red Spruce (Picea ruhens 

 Sargent), showing an early stage of the decay induced by the mycelium of Trainrtes 

 pini ( Brot. ) Fr. forma ahietix Karsten. The white spots indicate where the wood luus 

 been (rhanged so as to leave cellulose fibers. Small black lines are visible here and 

 there. 



Fig. 2. Radial view of Red Spruce log (natural size), showing advanced stage of the 

 same decay. The mimber of white spots has increased. Tlu' decay rarely goes 

 beyond this stage. 



PLATE VII. 



Radial view of a lug uf i'.alsain i'ir ( .lA/Vx Ixilsunird (!,. ) Mill.), shitwing advanced 

 stagi' iif ilccay due ti> '/'ndiuiis />iiii { ilnil. | l''i-. f<ii-iiia (thiilis Karsten. 



