53 



EXPLANATION OF PLATES. 

 PLATE I. 



Fig. 1. Rporophores of Polyporm schwemltzii Fr. 



Fh;. 2. A piece of the bark of Red Spruce with sporophores of Polyporus rolcatus 

 }\'ck jrrowin^' from holes formed 1)y a ])oring beetle, a species of Dendroctonus. 



PLATE II. 



Cioss section (Xf) of the trunk of a livino; youns: Balsam Fir {Abies hahamea (L. ) 

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

 schwelnltzii Fr., has shrunk the wood, producing 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?) of a log of White Spruce {Picea canadaisis (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 the center of the figure, which extend in an irregular 

 manner across the direction of the fibers. 



PLATE IV. 



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

 advanced stage of decay induced by mycelium of Polyporus 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 

 larva?, whose tunnels are filled with sawdust. 



PLATE V. 



Three sporophores (X-i) of Polyporus pinicoki (Swartz) Fr. The uppermost one 

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

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

 ridged ui)i)er surface is very marked. 



PLATE YI. 



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 Trametes 

 }>ini { Biot. ) Fr. forma ahietlx Karsten. The white spots indiciite where the wood has 

 l)een changed so as to leave cellulose fibers. Small black lines are visible here and 

 there. 



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

 same decay. The number of white spots has increased. The decay rarely goes 

 beyond this stage. 



PLATE VII. 



Radial vii'w of a log of P>alsam Fir (.1/^/V.s- Jirtlsarriea (L.) Mill.), showing advanced 

 stage of decay due to TrdimlcH pini ( lirot. ) Vv. forma ahittix Karsten. 



