. Diseases of deciduous forest trees. Trees -- Diseases and pests. SAP-ROTS OF SPECIES OF DECIDUOUS TREES. 59 results in their gradual destruction, ultimately causing the death of the entire tree. The injury to the wood is only local, occurring gen- erally near the base of the trunk. The fiuigus is said to enter the trunk through injuries near the ground line or through wounds on the roots, and "spreads upward through the entire wood, reaching, in specimens observed, the height of 10 feet. The entire wood of the lower portion of the trunk becomes thoroughly infected before the fungus obta
. Diseases of deciduous forest trees. Trees -- Diseases and pests. SAP-ROTS OF SPECIES OF DECIDUOUS TREES. 59 results in their gradual destruction, ultimately causing the death of the entire tree. The injury to the wood is only local, occurring gen- erally near the base of the trunk. The fiuigus is said to enter the trunk through injuries near the ground line or through wounds on the roots, and "spreads upward through the entire wood, reaching, in specimens observed, the height of 10 feet. The entire wood of the lower portion of the trunk becomes thoroughly infected before the fungus obtams sufficient vigor to produce its external fruiting bodies. In this condition the wood is rendered very brittle, and the tree thus affected is poorly fitted to withstand the force of the wind in severe storms" (38). The diseased wood is char- acterized by the appearance of numerous localized pockets, separated from one another by wood which the fungus has evidently not been able to de- stroy. Ileald states that the fungus is probably only a facul- tative parasite and "is not al)le to attack young, healths- trees, but that it can become parasitic on older trees in which the vitality has been consid- eral)ly lowered, or that have reached the maximum of their ; The writers have repeatedly observed this form of decay in the Cottonwood, but in their experience it usually starts near the base of the trunk in large wounds caused by fire or otherwise. On that account they are not inclined to call this decay of the Cottonwood a disease in the sense in which the decays induced by Fomes igniarius, F. fraxinopMlus, and others are diseases. There are a large number of species of fungi which, like FoTnes applanatus, grow on dead wood and which may now and then grow on living trees. All of these, including Fomes applanatus, can grow just as well and apparently better on wood after it has been cut from liv- 149. Fig. 8.—a dead stub of a maple tree bearing fruiting
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