DISEASED PELA BGONl U M 8. 



173 



different periods of its life-cycle. The first or uredo stage appears under 

 the form of minute snuff-coloured groups of spores arranged in miniature 

 fairy rings on the surface of the leaf. These uredospores are produced 

 in immense numbers, and are carried from one leaf to another by wind, 

 and thus enable the disease to spread with great rapidity. 



Later in the season, just before the leaves begin to fade, the production 

 of uredospores ceases, and a second kind of spore, called a teleutospore, is 

 produced from the same mycelium which earlier in the season gave origin 

 to uredospores. When the leaves decay, the teleutospores or resting - 

 spores lie unchanged on the ground until the following spring, when they 

 germinate and inoculate the young leaves, which in course of time again 

 bear first uredo- then teleuto-spores. 



Now Puccinia gramdaris is not uncommon on various kinds of wild 

 plants belonging to the Geraniacece, as Pelargonium aconitophyllum, 

 P. alchemilloides, &c, in Cape Colony, Transvaal, Natal, and Kaffraria, 

 and in all probability the fungus passed from such indigenous species to 

 the imported cultivated forms. 



The statement that the disease is worse in the case of plants grown 

 under glass than otherwise shows that such conditions of cultivation 

 result in "soft" foliage in South Africa as elsewhere. Is it possible to 

 grow plants under glass and yet retain the foliage as firm, crisp, and 

 resistent to fungi as when the same species is grown in the open air ? If 

 so, then those who do so will be no more troubled with those destructive 

 fungus epidemics peculiar to plants grown in hothouses, as all such are 

 only rendered possible by the flabby, limp, non-resistent foliage. In 

 other words, all such diseases are purely artificial creations called into 

 being by a combination of conditions, which at one and the same time 

 render the host very susceptible, and the fungus very aggressive. 



The prime factors in bringing about this condition of things are too 

 much moisture in the air and lack of proper ventilation. 



