200 ASCOMYCETES. 



envelops the needles and sends out haustoria similar to 

 Trichosphaeria parasitica (Fig. 90). 



Hcrpotrichia is, in high-lying situations, a very dangerous 

 enemy of young spruces, and nurseries in such places have 

 frequently to be abandoned owing to the death of all the 

 plants. Serious damage also frequently results in young planta- 

 tions where snow lies long and keeps the young trees pressed 

 down towards the earth. Then the fungus, even under the 

 snow-covering, weaves round and fixes the shoots so firmly 

 together, that only the healthy ones are able to free themselves 

 again and to resume their growth in spring. 



As preventive measures, nurseries should not be established 

 in high situations, nor in valleys where there is a large snow- 

 fall ; while in localities liable to attack, the planting of young 

 trees in basins or cups (hole-planting) should be avoided. The 

 loss from crushing-down by snow may be lessened by laying 

 trunks and branches of felled trees amongst the young plants, 

 and by going over them in spring, raising up all prostrated 

 plants. 



MELANOMEAE. 



Rosellinia. 



The perithecia generally occur in numbers together ; they 

 are black, and smooth or studded with bristles. The asci 

 contain eight oval, spindle-shaped, dark-coloured, one-celled 

 spores. Filamentous paraphyses are always present. 



Rosellinia quercina Hartig. 1 The oak-root fungus. This 

 fungus lives in the roots of oak seedlings one to three years 

 old, and causes the leaves and shoots to become pale and to 

 dry up. It spreads only during damp weather, especially 

 in June, July, and August. In wet years it may cause very 

 serious damage, especially in seed-beds. The mycelium pene- 

 trates into the living cells of the root-cortex, extending even 

 to the pith. At first the mycelium is hyaline, but later it 

 darkens, and the hyphae become twisted together into spun 

 thread-like strands the rJiizoctonia. These structures apply 

 themselves to roots of neighbouring plants, and soon enclose 

 them in a weft of hyphae ; by , this means the disease is 



1 R. Hartig, Untermich. am d. forstbotan. Institut zu Mi'mchen, Berlin, 1888. 



