114 PLANT DISEASES 



this species completely invests branches and young trees 

 in a dense weft. The lower branches of young trees 

 pressed to the ground by snow are often held in this 

 position by the mycelium. After the leaves are killed they 

 do not fall to the ground but remain anchored to the 

 branches by the fungus, and their surface becomes covered 

 with a brown felt of hyphae on which perithecia are 

 produced in considerable numbers. The fungus is met 

 with in elevated regions more especially, and grows actively 

 under the snow. 



Preventive Means. — Nurseries should not be formed 

 at high elevations, nor in valleys where the snow lies for a 

 long time. 



Hartig, Alleg. Forst. imd Jagd.^ Zeit. 1888. 



Prillieux, Maiad. des Plantes Agric, vol. ii. p. 212, figs. 



SILVER FIR LEAF DISEASE 



{Aaififhostigma parasiticuin^ Sacc . 

 Trichosphaeria parasitica^ R. Hartig.) 



This fungus is abundant in young fir-woods, attacking 

 more especially the silver fir [Abies pectinafa), less frequently 

 spruces. The mycelium is at first white, then yellowish- 

 brown, and covers the under surface of the branches. The 

 leaves are first killed, but do not fall to the ground, being 

 held to the branch by cobweblike mycelium. At a later 

 stage the twigs are also killed. In crowded woods the 

 mycelium passes readily from tree to tree, doing a con- 

 siderable amount of injury. The perithecia are formed 



