of sexual organs in Aecidium. 49 
creased in size and assumed a broadly obovate outline (Fig. 3). 
The hypha supporting the oogonium and immediately below 
it gave origin to a considerable number of lateral branches 
which grew up round the oogonium, and, along with the 
original weft of hyphae, forms the external covering of inter- 
laced threads enclosing the peridium during its development. 
On the third day the oogonium collapsed, when methyl-green 
revealed the presence of several small nuclei. The next phase 
of development consists in the oogonium becoming coarsely 
nodulose (Fig. 4), each nodule, with the exception of the basal 
row, eventually developing into a thick cylindrical basidium 
from the apex of which spores are cut off in succession by 
transverse septa, the oldest at the apex, the youngest at the 
base. The basal row of nodules develops like the others, but 
the adjacent rows of cells are agglutinated together and form 
the peridium (Fig. 5), which after dehiscence is reflexed, the 
component rows again separating from each other at the free 
margin. The growth of lateral branches below the oogonium 
after fertilisation recalls to mind what takes place in Peziza , 
as shown by Tulasne 1 , and also in the Florideae, whereas the 
development of a protective organ from the oogonium itself is 
rare, if not without parallel. The spores are capable of ger- 
mination the moment they become free in the peridium, and 
when placed in a damp atmosphere send out one, rarely two, 
germ-tubes, which may remain simple, but generally produce 
several lateral branches. The whole of the protoplasm and 
orange colouring matter passes from the spore into the germ- 
tube (Fig. 6). Spores sown on sections of tubers of Ranun- 
culus Ficaria germinated, the tubes entering the tissues of the 
tuber. Tulasne has pointed out 2 that when the spores of 
Aecidium rajmnculacearum are sunk in water, they do not 
germinate so readily as when placed in a damp atmosphere. 
During the past season, at the end of May, I placed a quan- 
tity of leaves bearing the Aecidium in question in a bottle 
1 Ann. Sci. Nat. ser. 5, Tome vi, p. 21 1, pi. 11-12. 
2 Sur les Uredinees et les Ustilaginees, in Ann. Sci. Nat. ser. 4, Tome 2, 
p. 127. 
E 
