PREVENTIVE AND COMBATIVE MEASURES. 79 



kind, whether from spruce, larch, pine or the silver fir, necessi- 

 tates removal of the bark, and probably cutting into the wood 

 itself. The exuded resin and naked wood dry up in course of 

 time and crack, thereby allowing the entrance of fungus-spores, 

 which germinate in the fissures of the wood and lead to its 

 destruction. 



The forests of spruce and fir in Bavaria furnish valuable 

 wood suitable for the manufacture of violins and other musical 

 instruments. Till recently the practice was first to split a test- 

 piece from the standing tree to ascertain the cleavage of the 

 stem. If the test did not split true, the tree was left standing 

 and wounded ; such stems naturally were soon attacked by fungi 

 (Polyporeae and Agaricini) and succumbed to some storm. 



The beech is frequently injured in a somewhat similar manner 

 by the woodmen, who hew out large pieces of the stem to obtain 

 material for wedges from the very tough occlusion- tissue which 

 is afterwards formed. Stems so damaged soon fall a prey to 

 Polyponcs fomentarius. Wounds to the wood are also frequently 

 produced during the felling of neighbouring trees, or as a result 

 of storms, or by the action of woodpeckers, ants, and other 

 enemies. In short, wounds are so common that the necessity 

 of practical remedial measures for closing them as entrances 

 for destructive parasites, must be at once evident. 



(2) Localities should be avoided which are known to pre- 

 dispose certain plants to disease. Just as one avoids cultivating 

 tender plants in cold situations, or planting our less hardy 

 trees in places known to be liable to frost, so ought we to 

 avoid the cultivation of plants in localities which will render 

 them more than usually liable to infection by fungi. Thus the 

 formation of spruce-nurseries at considerable elevations has had 

 to be abandoned, because it was observed that they were there 

 liable to complete destruction by Herpotrichia nigra. For 

 similar reasons the hole-planting of spruce in elevated situations 

 must be avoided. In moist localities nurseries of Douglas fir 

 and other trees are in danger of attack from Botrytis; while 

 close glass-houses and hot-beds are breeding-places for many 

 parasites which would at once die away with good ventilation. 



(3) The neighbourhood of plants which are supplemental 

 hosts of the same heteroecious fungus should also be avoided. 

 (See also p. 74.) 



