ROBERT HARTIG ON THE LARCH DISEASE. 23 



In muggy situations the larches soon become diseased, and die 

 in a few years without any large blisters making their appearance. 

 The cup-shaped ascocarps of the parasite appear upon the cortex. 

 It looks as though the large quantity of water present in larches 

 whose transpiration is interfered with greatly favours the develop- 

 ment and spread of the fungus in the wood, and that the disease 

 consequently spreads throughout the whole plant. 



The foregoing descriptive sketch of the results of my investiga- 

 tions may suffice to explain the recognised facts connected with 

 the occurrence and distribution of the disease. 



The larch-blister has been indigenous to high Alpioe regions 

 from time immemorial. It occurs, however, with marked in- 

 tensity only in damp muggy valleys in immediate proximity to 

 lakes {e.g., the Achensee in the Tyrol, etc.), though on plateaus 

 it may also destroy a small tree here and there. Owing to 

 the prevalence of air-currents, freely exposed ascocarps never 

 ripen on plateaus and valley-slopes. The ascocarps ripen only on 

 those blisters which are situated at the foot of the stem close to 

 the ground, or on blistered branches that are in contact with the 

 earth. This is owing to the surrounding high grass sheltering 

 the young ascocarps against air-carrents, and so keeping them 

 moist. 



In the early decades of this century, when the larch was 

 planted in various parts of Germany, the enemy was left behind 

 in its native habitat, and the trees flourished to perfection. Prob- 

 ably every old forester knows some groups of larches of the most 

 stately growth which date back to that period. In consequence 

 of these satisfactory results, the larch was generally planted 

 throughout the whole of Germany. Most excellent results were 

 obtained, even where the inferior quality of the soil held out but 

 a poor prospect of success. 



But after woods of all sizes had been established from the foot 

 of the Alps to the coasts of the North Sea and Baltic, the fungus 

 spread downwards from the Alps, to find everywhere the most 

 favourable conditions for its development. These consisted of 

 dense young pure woods, groups that had been formed in replant- 

 ing up old beech woods, moist stagnant air, wounds caused by the 

 moth, etc. Commerce also assisted to intensify the evil, diseased 

 larches being sent out from the nurseries and transported from 

 district to district. 



Under these conditions the fructifications of the fungus attained 



