POLYMORPHISM. 2.03 
tissues, produces an A’ cidium, 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 Atcidia 
contain, within a cellular membranous sac, a fructifying dise, 
‘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 A%cidium, 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 Restelia.t 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 Jate Professor @rsted instituted 
experiments, from which the same results ensued, as to dicidium berberidis and 
Puccinia graminis. See ‘‘Journ. Hort. Soc. Lond.” new ser. i. p 85. 
+ ‘Oversigt over det Kon. Danske Videns, Selskabs” (1866), p. 185 t. 8, 4; 
(1867,) p. 203, t. 8, 4; ‘Résumé du Bulletin de la Soc. Roy. Danoise des 
Sciences” (1866), p. 15 ; (1867), p.38; ‘‘ Botanische Zeitung” (1867), p. 104; 
‘Quekett Microscopical Club Journal,” vol. ii. p. 260. 
