PARASITIC FUNGI. 291 



of which give rise to zoospores, as first observed by Pro- 

 vost, in 1807. Like those of Peronospora, they move 

 about in water by means of two lash-like appendages, and 

 there germinate. When resting on the leaves of a plant, 

 they make their way by means of a germinating thread 

 into its subjacent tissues, and throw out little suckers. 

 The branched mycelium gives off sporangia and antheridia, 

 exactly as in Feronospora ; when ripe, the sporangia aru 

 strongly warted. They fall, doubtless, with the leaves to 

 the ground, where they remain till a fitting season arrives 

 for their development. The provisioii made for the rapid 

 development of these parasites and for the preservation of 

 their species is truly marvellous, and sufficiently accounts 

 for the difficulty of extermination and their apparently 

 sudden dispersion, especially in wet weather." 



De Bary's observations on the germination of Uromyces 

 api->endiculatu8 are interesting, inasmuch as they show that 

 the sporidia produce a mycelium, from which springs in 

 succession — 1st, spermogonia ; 2dly, peridia, producing 

 chains of orange-coloured fruit, or, in other words, an 

 uEcidium ; and 3dly, the original fruit of Uromyces, ac- 

 companied by the more simple fruit comanonly called 

 livedo, and now called ?6/'ec?o-stylospores. The germination 

 of the fruit produced by the peridia, as well as that of 

 the -ifrecZo-st^dospores, produces, according to De Barj^, 

 1st, ^refio-stylospores, and 2d, the original Uromyces- 

 spores. Thus we see the ZJrowyces-spores passing through 

 the generations of promycelium, sporidia, and mycelium — 

 the latter producing successively the two different products, 

 spermogonia and a3cidia, and ultimately the original fruit 

 of Uromyces, accompanied by the Uredo. The spermatia, 

 or contents of the spermogonia, never germinate ; but we 

 find the fruit of the ^ecidia, and also of the Uredo, repro- 

 ducing first the Uredo itself, and subsequently the original 

 fruit of Uromyces. Other interesting points, noticed by- 

 the same author, are, " that not only has each species of 

 parasite a certain special nutrient plant, but that in certain 

 XJredines with multiple fruit and alternate generations 

 each sort of rej^roductive organ buries its germ in a dif- 

 Jerent nutrient plant ; and that the vegetation of the para- 

 site is the cause of the disease." 



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