Abstract: The terpene tolerance of 16 species of Hymenomycetes occurring in nature in coniferous wood and that of 22 species growing in the wood of deciduous trees was studied by growing these on 1 % malt agar in closed desiccators into which measured amounts of the following terpenes were pipetted: α-pinene, β-pinene, limonene, camphene, or 3-carene. The corculation of the air within the desiccator was effected by means of a propeller. Most of the conifer species investigated were able to grow in the saturated atmospheres of these terpenes. In contrast, small amounts of terpenes already present in the air inhibited the growth of species occurring in the wood of deciduous trees. Judging from a survey of pertinent literature, the amount of terpenes in conifer wood is enough to saturate at least part of the atmosphere within living tree trunks. Evidently the terpenes in conifer wood have a selective effect on invading fungus populations through a “claustrogaseous effect” owing to the dense structure of the wood.