436 MR. A. W. BENNETT ON THE 
spore of Spiroyyra by Pringsheim *, reproduced in part in Sachs's 
‘Text-book’ (2nd English ed. fig. 170), the germinating filament 
is represented as proceeding from one end of the zygospore, and 
this whether germination takes place within the mother-cell or 
after the zygospore has escaped fromit. The same general direc- 
tion of growth is represented by Cleve (J. c. pl. i. fig. 3, & pl. vii. 
fig. 9), and less distinctly by Vaucher, De Bary, and others. In 
a zygospore of S. porticalis which I observed germinating while 
still within the mother-cell (fig. 4), the germinating filament 
was unquestionably proceeding from one side of the zygospore, 
and therefore at right angles to the previous direction of 
growth. 
The genera Mesocarpus and Staurospermum (together with the 
doubtful genus Craterospermum) are formed by De Bary into a 
distinct family of Mesocarpex, on the ground that, in his view, 
the product of conjugation is not a true zygospore which germi- 
nates directly, but more properly a earpospore which divides into 
a fertile resting-spore and several barren cells. Into the discus- 
sion of this interesting question I do not propose to enter. 
Mesocarpus differs from Spirogyra and Zygnema in two conspi- 
cuous characters. First, in the arrangement of the endochrome, 
which is well described by De Bary as forming an axile plate; 
that is, it is all collected in one plane passing through one dia- 
meter of the nearly cylindrical cell. Looked at, therefore, in 
Fig. 5. Fig. 6. 
Fig. 5. Mesocarpus scalaris, Hass. Cells showing axile plate of protoplasm: 
a, profile, 2, front view. X166. 
Fig. 6. Mesocarpus scalaris. Two cells in conjugation. X 165. 
what we may call the profile view (fig. 5a), the ehlorophyll 
appears to occupy a single narrow band passing across the cell ; 
but if the cell is turned through an angle of 90? so as to get the 
front view, the position in which the filament appears naturally 
to place itself on the glass slide (fig. 54), the appearance is pre- 
sented as if the cell were filled in the ordinary way with pro- 
toplasm uniformly pervaded by chlorophyll. In either case ? 
* * Flora, Aug. 14, 1852, pl. v. 
