CONTRIBUTIONS FROM THE WISLEY LABORATORY. 



513 



Cineraria or any of its allies. As in so many of the " rusts," it now 

 attacks a plant of a totally distinct family, *and produces disease either 

 on the Scots pine (Pinus sylvestris) or on P. austriaca, these two species 

 forming the hosts for the spring form of the fungus. The spores of 

 this spring form of the fungus on the pine needles are formed in little 

 white cups (aecidia) with torn white edges. Before they ripen these cups 

 appear like pale blisters upon the leaves. They are to be found in May 

 and June, and each contains large numbers of the aecidiospores, capable 

 of immediate germination and of attacking the Cineraria or one of the 

 species of Senecio, but not the pine. The fungus, as it occurs upon 

 the pine needles (fig. 93), is so different in appearance from that on the 

 Cineraria that it has been described under a different name and placed in 

 a different genus, being formerly called Pcridermium pini forma acicola, 

 but there is no doubt that it is only a stage in the life-history of a very 

 remarkable group of fungi. 



Ftg. 93.— Coleosporium senecionis on Leaf op Pinus sylvestris. 

 d, Aecidia ; e, Aecidiospores. (e much magnified.) 



Several other species of Coleosporium attacking other plants, e.g., 

 Sonchus, Euphrasia, and Campanula, have a form on pine needles which 

 cannot be distinguished from that belonging to C. senecionis by mere 

 examination even with the microscope ; but the aecidiospores of these 

 forms will attack only the plant from which the teleutospore, through 

 which the infection of the pine needles occurred, was derived. Thus the 

 aecidia produced as a result of infecting pine needles by the teleutospores 

 from Sonchus contain spores which only infect Sonchus, but not Senecio, 

 Euphrasia, Campanula, and so on. 



The injury to the plant arises from the fact that a certain amount 

 of the food manufactured for itself is withdrawn for the nourishment 

 of the fungus, and thus the whole plant suffers while at the same time 

 the leaves are disfigured. 



The fungus may be prevented from spreading by spraying the leaves 

 with a rose-red solution of potassium permanganate, and if watch is kept, 

 and this remedy applied as soon as any sign of the fungus appears, little 

 damage need be feared. 



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