192 THE NEW FORESTRY. 



ditions are correct. There seems to be no doubt now that 

 the disease is caused primarily by a fungus, Peziza wilkommii, 

 because experts claim to have proved that the disease can be 

 produced anywhere by innoculation. Granting this, Hartig's 

 theory of the spread of disease throughout Europe is probably 

 the right one. This theory, put shortly, is, first, that the 

 disease has always existed, but not to a destructive extent, in 

 the native habitat of the larch in high Alpine regions ; second, 

 that when the tree was first distributed throughout Germany, 

 Britain and elsewhere, the disease (not being propagated by 

 the seeds) was left behind in its native habitat and the trees 

 distributed flourished to perfection ; third, that after larch 

 woods of all sizes ■ had been established, from the foot of 

 the Alps to the coasts of the North Sea and the Baltic, afford- 

 ing a continuous line of communication, the fungus spread 

 downwards from the Alps to find everywhere the most 

 favourable conditions for its development. These consisted of 

 dense pure woods and groups, moist, stagnant air, and wounds 

 from various causes at which the disease entered. Preventive 

 measures, it is held, should consist in planting the tree, not in 

 pure woods, but in small proportion in mixed woods, and in 

 open airy situations (see Hartig's " Diseases of Trees " — 

 the larch). Hartig, arguing that fungi require much moisture 

 in the air to assist their development, thinks that the larch 

 fungus is almost certain to be worst in low-lying, damp situa- 

 tions, an opinion shared by some foresters, but open to doubt. 

 It is known, for example, that the conditions as regards rainfall, 

 moisture, and sunlight vary greatly in this country, and accord- 

 ing to Hartig's theory we would expect the disease to be most 

 virulent in wet districts and situations ; but that is not the 

 case, for in very dry localities the disease is found in its worst 

 form, and not always bad in wet ones. We have seen many 

 diseased plantations in England and Scotland, and the very 

 worst case we ever saw was in Norfolk, near the mouth of 

 the Wash, where the rainfall is about the lowest in England, 

 the situation dry, and the soil favourable, as indicated by the 

 health of older larch crops at the same place. A plantation, 

 about seven years of age, that had grown in that time to a 

 height of fifteen feet or more, was a mass of disease. The stem 

 of every tree was almost covered with blisters, which also 

 extended to the side branches up almost to the base of the 

 current year's growth. On branches four-and-a-half feet long, 

 as many as ten blisters, most of them well developed, might 

 be seen. In another and opposite case, in the north of 



