Warmth is also conducive to the growth of fungi, the most favorable temperature being about 90 deg.F.  They cannot grow in extreme cold, although no degree of cold such as occurs naturally will kill them.  On the other hand, high temperature will kill them, but the spores may survive even the boiling temperature.  Mould fungus has been observed to develop rapidly at 130 deg.F. in a dry kiln in moist air, a condition under which an animal cannot live more than a few minutes.  This fungus was killed, however, at about 140 deg. or 145 deg.F.[44]

[Footnote 44:  Experiments in kiln-drying Eucalyptus in Berkeley, U.S.  Forest Service.]

The fungus (Endothia parasitica And.) which causes the chestnut blight kills the trees by girdling them and has no direct effect upon the wood save possibly the four or five growth rings of the sapwood.[45]

[Footnote 45:  See Anderson, Paul J.:  The morphology and life history of the chestnut blight fungus.  Bul.  No. 7, Penna.  Chestnut Tree Blight Com., Harrisburg, 1914, p. 17.]

PARASITIC PLANT INJURIES.[46]

[Footnote 46:  See York, Harlan H.:  The anatomy and some of the biological aspects of the “American mistletoe.”  Bul. 120, Sci.  Ser.  No. 13, Univ. of Texas, Austin, 1909.

Bray, Wm. L.:  The mistletoe pest in the Southwest.  Bul. 166, U.S.  Bu.  Plant Ind., Washington, 1910.

Meinecke, E.P.:  Forest tree diseases common in California and Nevada.  U.S.  Forest Service, Washington, 1914, pp. 54-58.]

The most common of the higher parasitic plants damaging timber trees are mistletoes.  Many species of deciduous trees are attacked by the common mistletoe (Phoradendron flavescens).  It is very prevalent in the South and Southwest and when present in sufficient quantity does considerable damage.  There is also a considerable number of smaller mistletoes belonging to the genus Razoumofskya (Arceuthobium) which are widely distributed throughout the country, and several of them are common on coniferous trees in the Rocky Mountains and along the Pacific coast.

One effect of the common mistletoe is the formation of large swellings or tumors.  Often the entire tree may become stunted or distorted.  The western mistletoe is most common on the branches, where it produces “witches’ broom.”  It frequently attacks the trunk as well, and boards cut from such trees are filled with long, radial holes which seriously damage or destroy the value of the timber affected.

LOCALITY OF GROWTH

The data available regarding the effect of the locality of growth upon the properties of wood are not sufficient to warrant definite conclusions.  The subject has, however, been kept in mind in many of the U.S.  Forest Service timber tests and the following quotations are assembled from various reports: