52 
Henfrey, on some Fresh-water 
Apjocystis Brauniana, Nageli. 
Apiocystis, Nageli. Frond a microscopic, hyaline, gela- 
tinous, sac-like body, attached by an attenuated base ; contain- 
ing numerous green globular gonidia, multiplying, during the 
growth of the frond, by quaternate division, and finally breaking 
out by a lateral orifice as active, two-ciliated zoospores, each 
of which becomes encysted and grows up into a new frond. 
A. Brauniana, Nag. (PI. IV., figs. 26 and 27.) Frond 
pyriform, 1-600" to 1-25" high, the cavity filled up by gela- 
tinous matter, in which are embedded the gonidia, at first few, 
increasing in number with age as far as 1600, each about 
1-2000" in diameter. Nageli, ' Einz. Algen,' p. 67, PI. ii A ; 
KUtzing, ' Spec. Alg.,* p. 208. Fresh-water ditches, &c. 
A few young specimens of this little plant were observed in 
January of this year (1856) in a jar of water containing 
aquatic plants, brought from Wimbledon Common six months 
previously. The whole collection was destroyed by frost soon 
after, so that the development was not followed. Nageli {I. c.) 
gives the following account of it : — 
" The young ' swarm-cells ' (zoospores) attach themselves by their 
ciliated point (especially to Cladophora fracta), and become invested with 
a club-shaped enveloping membrane. The first division of the green 
body then takes place in the direction of the axis of the vesicular envelope, 
and is repeated, in A. Brauniana, alternately in each direction of space. 
During this the vesicle in which the cells (gonidia) lie, continually 
expands, and generally becomes very evidently pedunculated. Young 
vesicles contain a regular number of cells, namely, 2, 4, 8, 16, 32, &c. ; 
but the number afterwards becomes indefinite ; in largish vesicles, 1-50" 
long and 1-120" in diameter, I have counted about 300 ; in the largest, 
about 1-25" long and 1-50" thick, some 1600 cells. 
" The cells (gonidia) are at first uniformly distributed over the whole 
cavity of the vesicle. Subsequently they generally become collected on 
the internal surface of the wall of the vesicle, where they lie in one or 
more strata. But the cell-division always takes place in all directions 
of space, the cells situated internally advancing outwards towards the 
periphery. In old vesicles the cells are sometimes arranged in rings of 8 
upon the wall. 
" When the family of cells is mature for ' swarming,' which may occur 
at very different sizes and with very different numbers of gonidia, the 
cells begin to move at first slowly from their places, and then gradually 
to circulate more rapidly in and out about each other. The vesicle bursts 
and the gonidia emerge by the orifice which is formed. Sometimes the 
swarming is preceded by the state in which the cells are arranged in 
parietal rings. 
" The cells secrete an abundant gelatinous coating, which becomes 
softened within the vesicle, and confluent into a structureless jelly. The 
vesicle sometimes appears merely as the boundary line of the jelly ; in 
general, however, it may be distinguished as a distinct wall composed of 
denser gelatinous substance (PI. TV., fig. 25), the internal outline of which 
is always distinct and sJiarp, while the outer is frequently indistinct and 
partly dissolved." 
