66 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



infection, based on the experiments of Hartig and others, is that 

 the spores of the fungus, when shed, float in the air, and are 

 wafted from tree to tree, and that they find their way into the 

 young and tender bark through any wound they may meet 

 with, and there commence growth. I think it will be conceded 

 that, apart from questions of soil and aspect, the general opinion 

 of planters is that isolation of the larch, by treating it as a 

 subordinate species in mixture with other kinds, is the only 

 practicable precautionary measure which can be adopted 

 against attack by the fungus. But what have we here ? The 

 whole area covered by a series of lines of larch plants, 3^ 

 feet apart, which, from a preventive point of view, are in no 

 better a position than a pure larch plantation would be, and 

 this is done apparently because the authors of the plan think it 

 essential to have the plants in lines in order that the forester 

 may be able to control thinning operations ! There is an 

 undoubted advantage in planting in lines for easier control, and 

 in practically no other case can any objection be urged against 

 it ; but surely it is courting disaster to do this with larch in 

 the way suggested here ? The whole area on which larch is to 

 be grown is to be covered with a series of infecting lines, and 

 if it be the case, as some believe it to be, that Chermes laricis 

 is a potent factor in the spread of the disease, the danger is 

 greatly accentuated in the case of the larch and spruce mixture 

 by the presence of the two host-plants necessary for the insect 

 to complete its life-cycle. If larch is to be used, why not give 

 it a fair chance to succeed ? Where lines of larch and lines of 

 Scots pine alternate, what is the objection to planting larch and 

 Scots pine plants alternately in the lines in which it is proposed 

 to plant larch only, and thus reduce the proportion of larch to 

 Scots pine from one-half to one-quarter ? or, what would perhaps 

 be better, where two lines of Scots pine alternate with one line 

 of larch, to make every third plant only a larch plant in the 

 proposed lines of larch, and thus reduce the proportion of larch 

 to Scots pine from one-third to one-ninth ? It would give all 

 the advantages of easier control, would isolate the larch plants,, 

 and would give far better protection to the soil. 



