74 PREVENTIVE AND COMBATIVE MEASURES. 



deficient modes of conveyance, and a small demand for the 

 thinned-out material, this may appear impracticable. I shall 

 give one example how the number of " fungus-sponges " (as 

 the sporophores are called) decrease with enclosure and intro- 

 duction of proper forest-management.^ Bischoffsreut is a forest 

 in Bavaria, near the Bohemian frontier, consisting of mixed 

 spruce and fir up to four hundred years, and beech up to 

 two hundred. Forty years ago the sporophores of Polyporus 

 fomentarius, the tinder-fungus, were so numerous and large that 

 for their collection for manufacture of caps, gloves, tinder, etc., 

 a sum of one hundred gulden (£8 10s. Od.) was paid annually 

 as rental. Ten years ago the same brought in a revenue of 

 twelve shillings ; to-day it is free. In course of time the 

 diseased stems have been gradually felled and less wood has 

 been allowed to remain lying in the forest to decay ; as a 

 result the wood-destroying fungi have now but little foothold. 

 A mixed damp virgin forest is especially favourable for the life 

 and distribution of fungi of this kind.^ All fallen wood remains 

 lying, while injuries from storm afford easy spots for infection. 

 In Bischoffsreut eighteen per cent, of the felled heavy wood 

 was at one time useless and rotten. 



(2) It is often possible to avert diseases of valuable cultivated 

 plants caused by heteroecious fungi, by keeping the supplemen- 

 tary host at a distance, or, if the disease has already broken 

 out, to remove it altogether, with the view of keeping the 

 more useful host free from the dreaded disease. 



The best example of this is presented by the heteroecious 

 rust-fungus GymnosiJorangium sahinae. One host frequents 

 Junij^crus sabina (savin), the other damages pear-trees, causing, 

 in the case of a severe attack, considerable loss. It would thus 

 be easy to exterminate pear-rust by removing the not very 

 decorative savin-bush. Particularly in nurseries, it would be 

 well to avoid placing pear-trees near the savin, an arrangement 

 very suitable for cultivating the Gymnosporangium. 



As another example we may take Mclampsora tremulae 

 frequenting the aspen, the supplementary host of (a) Caeoma 

 pinitonpiiim (the pine twister), and ih) Caeoma laricis (larch 



^ V. Tubeuf, "Mittheilung iib. einige Feinde d. Waldes." Alleg. Forxt.-u. 

 Jagdzeitunij, 1887. 



-V. Tiil)eiif, " Vegetationsbilder,- aus d. boehinischen Urwalde." Oeste^-reich, 

 Forslzeiluwj, 1890, p. 108 ; with six figures. 



