Dec. 1, 1924 
Diagnosis of Decay in Wood 
541 
Fig. 3—A—Section of jack pine (Pinus banksiana ) railroad tie treated with creosote showing areas where 
sections were taken for microscopical examination. Area a is the typical stage of brown rot produced 
by Lentinus lepideus, which apparently entered the tie after it was laid in the road bed. Area b represents 
the very faint yellowish-brown area surrounding the typical rot. The remaining area up to the creosoted 
portion is normal in color. Presence of hyphae is indicated by + , hyphae not observed by 0. The 
distance from the edge of the plainly visible color in A to the center of No. 9 is 3 T a ff inches. B— Section 
of young tree of Populus tremuloides infected with Fomes igniarius. a, typical stage of rot; b, incipient 
c, very faint yellowish discoloration bordering on b. Hyphae were observed in 1 to 7 and in the margin 
of 8. From edge of area b to nearest edge of 8 is three-fourth inch. From edge of b to edge of c, longi¬ 
tudinally, is 2^ inches. C.—Section from living tree of Abies balsamea infected with Polyporus bal- 
sameus. Typical rot at a, incipient rot at 6, with edge of faintest discoloration shown by dotted line. 
Sapwood region at c limited by straight dotted line. Cultures were made as indicated by numbers and 
positive results obtained from numbers 6 to 14, inclusive. Cultures from 6, 7, and 8, taken from appar¬ 
ently sound wood, are positive; cultures taken from the sapwood region are negative. No hyphae were 
observed in the sapwood. D.—Section of young tree of P. tremuloides infected with F. igniarius . Light 
shading represents typical rot, heavy shading the brown invasion zone. A zone line is shown at the 
bottom. Positive cultures were secured from the typical rot area and from one fragment taken from 
the invasion zone area. The areas showing no discoloration gave negative cultures. E.—Section from 
living tree of Abies balsamea infected with P. balsameus: a, buff yellow to brownish typical rot area, 
b , incipient faintly colored rot area. Sections for examination were cut as indicated. Hyphae were 
observed in all the sections and were fairly numerous in 4 and 5 which were taken from the normal colored 
wood. Distance from 1 in typical rot to 3 in incipient is 2ff inches. Distance from edge of b to center 
of 5 is 1% inches. 
