WITCHES-BROOM. 447 



This fungus alternates as Melampsora Tremulae, Tul., on 

 the leaves of the aspen, which produces resting-spores or 

 teleutospores ; these hibernate on the dead aspen leaves, and 

 produce promycelia in the spring from which spores develop, 

 which then infect young pines. Eostrup first discovered, in 

 1883, that Caeoma spores generated on aspen leaves. 



b. Subjects of Attack, and Distribution. 



This fungus attacks chiefly young one to ten years old- 

 Scots pine, also Weymouth and mountain pines, but never 

 trees over 30 years old ; it is most frequent on damp soils, and 

 in cold, moist, early summers. The exemption of older pines 

 from the attacks of this fungus is probably due to the fact 

 that the spores proceed from dead aspen leaves lying on the 

 ground. 



One to three years old cultivations of pines may be entirely 

 destroyed by it, the disease spreading centrifugally from a 

 centre of infection ; and in older woods, especially after a 

 succession of rainy years, such misshapen stems may be formed 

 that the marks of the damage always remain patent ; the 

 development of the malady is however retarded by dry weather, 

 and the disease disappears about the thirteenth year. This 

 disease is known all over Germany, especially in the north, 

 and did great damage between 1870 and 1873. For attacks 

 by M. Tremulae, Tul., on larch needles, vide p. 469. 



c. Protective Measures. 



Careful choice should be made of suitable localities for 

 growing Scots pine. 



Immediate pruning and burning of infected shoots should 

 be effected. 



Remove aspen from pine woods. 



Witches-broom. 



Witches-broom is an abnormal hypertrophy of twigs appear- 

 ing on manj^ broadleaved and coniferous trees, and is caused 

 by the action of animals as well as of plants. 



