36 JOURNAL OF FORESTRY 



areas where the action of the sun and wind soon removes the required 

 moisture from the. wood tissues, and thus completely checks the 

 development of the disease within. In many cases where the above 

 conditions exist it often happens that a more xerophytic fungus is 

 able to secure a foothold in the dead host and successfully develop 

 fruiting bodies. In this manner the moisture factor in a large measure 

 restricts the activities of the less xerophytic fungi and favors the 

 xerophytic types. 



The majority of literature dealing with wood rotting fungi records 

 that the resin formed by the host acts as a protective element as well 

 as a means to resist the advance of the mycelium within the host 

 tissues. Resin also plays an important part on certain hosts in pre- 

 venting the development of sporophores and causing the production 

 of abortive ones. In western white pine, western larch, and other 

 conifers attacked by Trametes pini, resin flows, and swellings at 

 branch whorls are characteristic symptoms of a diseased condition 

 within. The flows and swellings are outward indications of the 

 reactions of the host to the activity of the fungus in certain branch 

 knots, and prevent, to a certain extent, the production of fertile 

 sporophores. Digging into these branch knots with the corner of an 

 axe or hatchet reveals underneath the resin coating a mass of brownish 

 mycelium of the same context as the sporophores of T. pini. Small 

 abortive sporophores are thus produced at the branch whorls, and 

 these rarely recover sufficiently to produce a hymenial surface and 

 spores. Very often these abortive sporophores take on peculiar shapes, 

 the most interesting have been of Echinodontimn tinctorium and 

 Trametes pini.^'^ 



Sporophores developing on dead and down timber have no live 

 sap zone to prevent their emergence upon the host surface. The air 

 supply is at least greater than when the tree was live and standing, 

 and the only factors influencing the development of sporophores are 

 the factors of food and moisture supply, and such external factors as 

 may prevent their appearance on the surface of the host. Moisture 

 is by far the most important influence, for without sufficient moisture, 

 even if food and sufficient air were present, the development of the 

 fungus is bound to be checked. 



It has been noted that remarkably fewer fruiting bodies appeared 

 in the forests during the exceptionally dry years than in the years in 

 which rain was plentiful. This fact tends to show that lack of moisture 

 due to continued high temperatures reduces the sporophore production 

 appreciably. 



