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The ^cidium Stage of Uromyces Pisi on Euphorbia 

 Cyparissias. 



By J. W. Reed. 



{Read March ISth, 1898.) 

 Plate 6. 



During some readings in Kerner's " Natural History of Plants" 

 just before my last annual holiday in the Alps, I specially noted 

 a passage referring to the metamorphosis produced by the 

 parasitism of Uromyces jnsi, in its -^cidium stage, in one of the 

 Spurges growing freely at Saas-Fee in the Canton Yalais. 



The Spurge in question was the Euphorbia Cyparissias, a 

 Central and Southern European species, and only known in 

 Britain as a cultivated plant, though in some places it has escaped 

 and partially established itself. Last summer, as in that of 1896, 

 my mountaineering companion was Mr. George Nicholson, the 

 Curator of Kew Gardens, and on our arrival at Saas-Fee we 

 began without delay a search for healthy and infected plants of 

 the Euphorbia ; nor had we far to seek. The mounted specimens 

 exhibited this evening are average samples of what came under 

 our notice. Only the most cursory examination of these plants 

 is necessary to show the extraordinary changes induced in the 

 tissues, colour, and general habit of this Spurge — changes so great 

 that diseased and healthy plants would scarcely be recognised as 

 belonging to the same species or even genus. 



It will be seen at a glance that whilst in the non-infected 

 plants the leaves are thin, linear, and of a somewhat deep green, 

 the whole habit being bushy, in the diseased ones the leaves are 

 short and thick, the colour a dusty yellow, and the stems look 

 naked and stalky, and do not branch. I have measured the 

 healthy leaves, and find them from seven to fourteen times as 

 long as they are broad ; the leaves with ^cidia are only about 

 four times as long as broad, and are placed more widely apart 

 than are those of the normal Euphorbia. Elongation of the stem 



JouRN. Q. M. C, Series II., No. 43. 5 



