BRITISH FOREST TREES 257 



the foliage ; caterpillars of Zeuzera asculi and Cossus 

 ligniperda, and to a slighter extent larvae of Anobium tessela- 

 tum and Hylecoetus dermestoides, injure the quality of the 

 timber. 



Fungoid diseases of the stem are originated by Nectria 

 ditissima and N. cinnabarina, the latter with characteristic 

 bright vermilion gonidia, which subsequently turn darker. 

 As with other trees, Phytophthora omnivora infects the seed- 

 lobes and leaves in nurseries. The curious black spots so 

 frequently seen on leaves is a disease caused by Rhytisma 

 acerinum ; it is much more common in parks and orna- 

 mental woods than in true forests, but should be treated 

 as a disfigurement of the foliage, and encountered by collect- 

 ing and burning the leaves in autumn and winter in order to 

 prevent the scattering of the spores and the spread of the 

 disease during the following spring. 



The Sylvicultural Treatment of Maple and Sycamore re- 

 sembles in most points that accorded to the ash and the 

 elm. They are not naturally intended to be grown in pure 

 forests, or even to be allowed to grow up in clumps or 

 groups, as they are distinctly light-loving after they have 

 passed through the pole-forest stage of growth ; hence they 

 soon exhibit a tendency towards branching and sparse crown, 

 and with their scanty broken canopy, and light annual fall 

 of foliage, prove unable to protect the soil against ultimate 

 deterioration. Scattered here and there, however, and 

 interspersed as single stems, or in occasional small knots or 

 patches throughout woods of other species, that are more 

 efficiently endowed by nature with soil-protecting qualities, 

 they develop into valuable timber trees, and often yield 

 very handsome returns where there is a good market for 

 furniture woods. 



Like other species of trees that are beyond all doubt light- 

 loving, maple and sycamore can stand a considerably greater 



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