MELAMPSORA PINITORQUA 57 



any leaves of Ribes to which they may be carried, thereby 

 forming a means of rapidly spreading an infection which is 

 once started. After a few weeks, brownish thread-like growths 

 appear in the uredo-sori : these are the filaments on which the 

 teleutospores are borne, and the latter may be found from July 

 until the fall of the leaf, and even upon the fallen leaves. The 

 teleutospores may germinate at once, perhaps also after a con- 

 siderable time, but the basidiospores which they produce can 

 only infect young branches of Pine as described above. They 

 are distributed by the wind, but probably cannot be carried to 

 any great distance. Owing to the long incubation period of 

 the mycelium which will produce the secidiospores, the fungus 

 cannot be seen on the Pine until it is at least three years old, 

 although infection may have taken place in the seedling : by 

 that time the leaves have naturally fallen off the part which 

 received the infection. 



Though this disease does little harm to the currant, it is 

 necessary to destroy the infested bushes, since they form a focus 

 of infection for the Pines. Weymouth Pines that are more 

 than 20 — 25 years old are rarely liable to attack. 



Melampsora pinitorqua. 

 The Pine and Aspen Rust. 



The secidial stage of this Melampsora lives on young shoots 

 of Scots Pine (Pinus silvestris) and its uredo- and teleuto-stages 

 on leaves of Aspen (Poptdus tremula). 



The teleutospores germinate after a winter's rest, and the 

 basidiospores infect the young pine-buds, just beginning to 

 elongate in May and June. The mycelium produced penetrates 

 the cortex, and reaches also the bast and medullary rays. On 

 these shoots the spermogones appear about the end of May, 

 and are followed by the secidia. The cortex of the affected part 

 becomes orange and dead, while the unaffected part still con- 

 tinues to grow. Thus thin shoots may be killed altogether, 

 but in the thicker ones curvature takes place owing to the 

 one-sided growth : the negative geotropism of the growing 



