66 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



of western North America. Both species attain a large size 

 in their natural habitats, and the timber has a wide range of 

 uses. A fungous disease {Cronartinm ribicolum) has caused 

 serious damage to these species both in this country and 

 elsewhere in Europe, and has greatly limited their use. This 

 disease is now a serious one in America. It is believed 

 that it was imported from Europe. There are several young 

 plantations in this country which are so far free from disease 

 and are showing good growth. In Germany the disease was 

 found to be less serious on certain soils, and it should be a 

 matter for experiment in this country to determine under what 

 conditions, if any, we can grow this valuable conifer. 



LARCHES (Larix). 



Two species of larch are, at present, of importance in forestry 

 in this country, viz. European larch and Japanese larch. 



European Larch (Larix Eur oped). 



This species was introduced about two centuries ago into this 

 country from the mountains of Middle Europe. Larch trees 

 which were planted in the early years of the eighteenth century 

 are to be found growing in various parts of the country — one 

 of what were known as the "Parent Larches" still stands at 

 Dunkeld. 1 



Although the natural habitat of the larch is the mountains, 

 it has been planted in this country under all possible conditions. 

 The effect of the planting of this species under unsuitable con- 

 ditions, and probably also by keeping the plantations too dense, 

 has been to weaken its resistance to disease. Larch now suffers 

 from a very serious fungous disease known as larch canker or 

 blister (Dasyscypha Willkomii). As this disease has an important 

 bearing on the various problems connected with larch, it will be 

 briefly considered at once. This fungus is what is known as a 

 wound parasite, i.e. infection is by means of spores through 

 wounds in the host. The spore or spores germinate, grow, and 

 destroy the vital tissue lying immediately beneath the bark. 

 The exudation of resin is the first obvious symptom of the 

 disease. The successive cutting-off of the destroyed tissue by 



1 Schotte's views in regard to the Scottish type of larch are discussed 

 in Mr Murray's summary of the Reports of the Swedish Forestry Research 

 Institute, in this issue, p. 98. 



