240 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



menced tliis article on the Douglas fir in Scotland, I saw in a 

 German forest journal, a notice of the discovery of an injurious 

 fungus on the Douglas fir. Dr von Tubeuf, a pupil of the 

 celebrated pathologist, Dr R. Hartig of Munich, has now described 

 a fungus, Botrytis Do%iylasii, which is parasitic on the Douglas fir : 

 it has been noticed during the last ten years, in several widely 

 separated localities in Germany, on the trees in the experimental 

 plantations which have been made of late years. As far as is 

 known at present, the fungus attacks in the first place tbe young 

 shoots, the needles of which turn brown or grey, the whole being 

 ultimately spun over with mycelium ; it then extends and ultimately 

 kills the plants. It has alst) been found that this same fungus can 

 be cultivated on two to six years old plants of silver tir, spruce, 

 and larch. Dr von Tubeuf found, as a geneial rule, that those 

 Douglas firs were specially attacked which grow in fully stocked 

 areas, so that the branches of the trees interlaced ; and in these 

 cases the lower branches were more attacked than those higher up. 

 He also noticed that free standing trees were free of the disease, 

 and he naturally draws the conclusion, that infection depends on a 

 high degree of moisture, such as is found in dense woods, while 

 free-growing trees, exposed on all sides to drying air currents, 

 escaped. Now, what does this mean 1, Simply that the Douglas 

 fir must be grown in thin open woods, and if so, good-bye to any 

 high returns per acre, such as silver fir, larch, or even Scots 

 pine will yield. 



Generally, Dr von Tubeuf adds some very sensible remarks, of 

 which I give the following extracts. He says : — 



" In introducing an exotic species, the first question should be 

 whether, if grown in the same locality, it possesses any real 

 advantages over our indigenous species, either in consequence of a 

 superior quality of wood, rapid growth, large dimensions, active 

 reproductive power, etc., or by more successfully resisting any 

 unfavourable conditions of the soil or climate, or by being less 

 subject to natural enemies, such as game, animal or vegetable 

 parasites, etc. ? A further most imj)ortant question is, whether with 

 the exotic tree we are likely to introduce new enemies to our 

 indigenous trees ? and in this respect we need only remind the 

 reader of the imported enenues of the potato, the Colorado beetle, 

 the enemies of the vine, etc. 



" Of our own enendes of trees, a large number attack without 

 distinction the exotics lately introduced — Curculio, Bostrychus, 



