POLYMORPHISM. 203 



tissues, produces an JEciJium, with its constant companion, sper- 

 mogonia distinct cysts, that is, from which a quantity of minute 

 bodies ooze out, often in the form of a tendril, the function of 

 which is imperfectly known at present, but which from analogy 

 we regard as a form of fruit, though it is just possible that they 

 may be rather of the nature of spermatozoids. The JEcidia 

 contain, within a cellular membranous sac, a fructifying disc, 

 which produces necklaces of spores, which ultimately separate 

 from each other in the form of a granular powder. The grains 

 of which it is composed germinate in their turn, no longer 

 avoiding the stomates as before, but penetrating through their 

 aperture into the parenchym. The new resultant mycelium 

 reproduces the Uredo, or fifth form of fructification, and the 

 Uredo spores fall off like those of the JEcidium, and in respect 

 of germination, and mode of penetration, present precisely the 

 same phenomena. The disc which has produced the Uredo 

 spores now gives rise to the resting spores, and so the cycle is 

 complete.* 



The late Professor CErsted, of Copenhagen, was of opinion 

 that he had demonstrated the polymorphy of the Tremelloid 

 Uredines, and satisfied himself that the one condition known as 

 Podisoma was but another stage of Rcestelia.f Some freshly 

 gathered specimens of Gymnosporanqium were damped with 

 water, and during the night following the spores germinated 

 profusely, so that the teleutospores formed an orange-coloured 

 powder. A little of this powder was placed on the leaves of 

 five small sorbs, which were damped and placed under bell- 

 glasses. In five days yellow spots were seen on the leaves, and 

 in two days- more indications of spermogonia. The spermatia 

 were discharged, and in two months from the first sowing, 



* Almost simultaneously with De Bary, the late Professor CErsted instituted 

 experiments, from which the same results ensued, as to jKcidiam, berberidis and 

 Puccinia graminis. See "Journ. Hort. Soc. Lond." new ser. i. p 85. 



t "Oversigt over det Kon. Danske Videos. Selskabs" (1866), p. 185, t. 3, 4; 

 (1867,) p. 208, t. 3, 4 ; " Resume du Bulletin de la Soc. Roy. Danoise des 

 Sciences" (1866), p. 15 ; (1867), p. 38 ; " Botanische Zeitung" (1867), p. 104 ; 

 " Qnekett Microscopical Club Journal," vol. ii. p. 260. 



