Weir: Altitudinal Range of Forest Fungi 9 



regularly increases with increase in elevation with exactly the 

 reverse for the mineral substances. With increasing elevation, 

 certain anatomical changes in forest trees such as narrower rings 

 imparting a hard flinty condition to the heartwood, 5 tend to reduce 

 their disposition to disease. The influence of high mountain 

 conditions on the prevalence of fungi is more noticeable in the 

 case of leaf and twig diseases because of certain modifications 

 of the host which makes attack by parasites difficult. The foli- 

 age of forest trees and other plants at high elevations is usually 

 greatly modified to withstand arid conditions. This modification 

 is generally expressed by a thicker epidermis, excessive develop- 

 ment of hairs and waxy coverings and, no doubt, retards and in 

 many cases absolutely prevents infection. Very few endophytic 

 leaf parasites have been collected at high elevations. On the 

 other hand, epiphytic species are more common. With the re- 

 verse of these conditions in the lowlands the same species may be 

 and usually are more seriously attacked by fungi. The diffi- 

 culty experienced in the cultivation of the larch in the lowlands 

 of Germany owing to the increased destructiveness of Dasyscypha 

 Willkommii Hartig is a case in point. 



Any forest tree with a great altitudinal range is more severely 

 attacked by fungi at its lowest elevation. As examples, grand fir 

 {Abies grandis Lindl.), western hemlock (Tsuga heterophylla 

 (Raf.) Sarg.), and alpine fir, particularly show this to be true. 

 The problems of management with regard to forest tree diseases 

 in the highest elevations at which merchantable forests can be 

 grown will never be as difficult as at lower levels. The fact that 

 the tree species will be more or less separated into their com- 

 ponent types will not at this elevation be as serious a factor in 

 promoting the spread of fungous diseases as at lower elevations. 

 The big problem at low elevations in reducing the ravages of 

 fungi is to find the environment best suited for the several species 



Einfluss des Standortes auf den Aschengehalt des Buchenlaubes. Allgem. 

 Forst.- u. Jagdzeitung. P. 221. 1875. 



Also Cieslar, A. Uber den Ligningehalt einiger Nadelholzer. Mitt. a. d. 

 Forst. Versuchswesen Osterreichs. v. 23: 1897. 



5 Rosenthal, M. Uber die Ausbildung der Jahresringe an der Grenze des 

 Baumwuches in den Alpen. Cit. Bot. Centralbl. nr. 43. 1904. Sendtner, 

 Vegetationswerk. Sudbayerns. P. 555. 



