Dec. 1 , 1924 
Diagnosis of Decay in Wood 
547 
Fig. 5.—A .— Polyporus balsameus in Abies balsamta. Typical stage of rot. Radial section through heart- 
wood. a, Constriction of hyphae in passing through cell wall, b, c, bore holes produced by hyphae. 
B.—Radial section through heartwood of Pinus strobus infected with Trametes pini. Section taken 
near edge of white pocket, a, An older hypha of a brownish color showing the habit of constriction 
when passing through the cell walls; b, a young hypha, hyaline, and branched (the constriction of the 
thread does not appear in these young hyphae); c, characteristic clamp connection often found in wood 
infested by this fungus; d, tangled masses of apparently anastomosed hyphae; e, bore hole with fungus 
thread dropped out; /, embossed portion of bordered pit entirely decomposed. The effect on the middle 
lamella allows a separation of the individual cell walls. C. —Tangential section through the heartwood 
of Tsuga heterophylla infected with Echinodontium tinctorium. Section from typical stage of the rot. 
The general character of the dissolution of cell walls may be noted, a, an older hypha penetrating several 
cells walls and showing slight constrictions on passing through .the bore holes; b, bore holes made by the 
hyphae in passing through the cell walls; c, characteristic clamp connection not often observed in the 
decayed wood; d, dissolution of the medullary ray and portions of the lignified cell wall of the tracheid. 
D.—Tangential section through the heartwood of Picea canadensis infected with Trametes carnea. Sec¬ 
tion taken from the edge of typical stage of the rot. a, hypha penetrating several cell walls and showing 
no constriction in passing through the walls. In this case the bore holes are usually much larger than 
the hyphae; b, characteristic bore hole with hyphal thread dropped out; c, this type and the simple 
type of clamp connection are frequently observed in the infected wood; d, peculiar uncommon form of 
shrinkage cracks found in the typical stage of rot. The spiral form of shrinkage crack is absent; e, very 
minute hyaline hyphae are often observed. The bore holes produced by these hypha are also larger 
than the hyphae. E.—Radial section through the heartwood of Pinus banksiana infected with Leniinus 
lepideus. Section from early typical stage of the rot. a, Hyphal thread penetrating tracheid cell wallse 
one of the very large and characteristic bore holes is shown at b, where the irregular surface of the bor; 
can be noted; c, a peculiar type of medallion or detour hypha commonly found in this material; d, spiral 
shrinkage cracks ascending from right to left and extending as far as the middle lamella of the cell wall. 
F.—Radial section through the heartwood of Libocedrus decurrens infected with Polypor us amarus . 
Section from the edge of the pocket of brown cubical rot. Hyphae are generally scarce in this rot. a. 
Large hyaline hypha penetrating several tracheid cell walls which show roughened surfaces due to the 
action of the fungus (the hypha is constricted in its passage through the walls); b, minute hyaline hyphae 
are occasionally observed and these appear to be slightly smaller than the bore holes they produce; 
c, hypha showing clamp connection; d, bore hole, showing the even smooth surface; e, spiral shrinkage 
cracks ascending from right to left are common in the typical stage of the rot and appear to be more 
numerous in the cells of the summer wood. The bordered pits show evidence of the fungus action and 
cases may be noted where little is left to indicate the original location of the bordered pit. 
Fig. 6.—Penetration of hyphae of Trametes pini through tracheid cell walls of Pinus strobus is shown in 
1 to 12. (The older, larger, brown hyphae in 1 diminish in size to the small hyaline hyphae shown in 
10.) An oblique cut through hypha and bore hole, rather than the early stage of penetration, is shown 
in 11. Surface view of a hypha passing through a bore hole is shown in 12. The diameters of the bore 
holes vary but little. Radial section of Pinus ponderosa infected with Polyporus anceps (P. ellisianus) 
shown in 13. Incipient stage of rot, showing size of bore hole and constriction of the hyphae. The bore 
holes made by the very small hyphae seem to be larger than the hyphae. A spore-chain formation of 
the hyphae is often observed as shown in the drawing. Radial section of Tilia americana infected with 
Pholiota adiposa is shown in 14. Incipient stage of rot secured by inoculating a sterilized block with a 
pure culture of the fungus. The hyphae are slightly constricted in passing through the cell walls. 
Tracheid wall of Picea sitchensis infected with Polyporus schweinitzii , from the typical rot area, shown 
in 15, with penetration by hyphae and types of bore holes. Slight constriction qf the hyphae in the larger 
threads (d) . The bore holes are irregular and constricted at the middle lamella (c and e) . Bore holes 
accompanying the very small hyphae seem larger than the threads passing through them. Radial 
section of Populus balsamifera infected with Fomes igniarius shown in 16. From the invasion zone area 
near the edge of the typical rot. a, One of the minute hyaline hyphae passing through bore holes in the 
cell walls of the wood fibers; b, one of the larger hyphae passing through the walls. The bore holes are 
very much larger than the hyphae; c, typical bore holes showing the greater resistance to dissolution 
exhibited by the middle lamella. Radial section of Pinus banksiana infected with Lentinus lepideus is 
shown in 17. From the faintly discolored area near edge of typical rot. Young hypha (a) and older 
hypha (ft) passing through cell walls; c, type of bore hole showing constriction at middle lamella; d, 
characteristic “detour” or “medallion” hypha frequently found in this material. Radial section of 
Betula papyrifera infected with Polyporus betulinus is shown in 18. From typical rot area, showing pene¬ 
tration, size, and shape of bore holes. Radial section of Betula papyrifera infected with Fomes fomentarius- 
is shown in 19. From near edge of typical rot area. The bore holes are of typical “hourglass” shape. 
Radial section of Tsuga heterophylla infected with Echinodontium tinctorium is shown in 20. From the 
early typical stage of rot. No constriction of the hyphae nor of the bore holes was observed, a, Older 
hypha with young branch at b showing penetration through the pit membrane; c, bordered pit showing 
action of the fungus in dissolving the embossed portion. Radial section of Robinia pseudoacacia L. 
infected with Trametes robiniophila (P. robiniophilus) shown in 21. From typical stage of rot, showing 
penetration of the tylose walls in the pore cells by the hypha. The bore holes are larger than the hypha. 
Semidiagramatic view of the bordered pit in the tracheid wall of Pinus strobus is shown in 22, with the 
hypha of Trametes pini passing through the wall at a and through the bordered pit at b. Older hypha 
(a) and young hypha ( b ) of Trametes pini passing through cell walls in P. strobus are shown in 23. Radial 
section of Libocedrus decurrens infected with Polyporus amarus is shown in 24. From edge of rot pocket.. 
Penetration and characteristic constriction of older hypha and type of bore hole appear. 
