Notes . 
4i5 
If the cultures containing such germinated zoospores were retained 
for some days, the successive generations of zoospores, derived from 
the first individual, showed a gradually decreasing scale of develop- 
ment. Thus the zoospores liberated from the fully-developed 
unicellular plants, described above, on coming to rest and germinating 
did not form nearly so long a root, nor was the tip fully developed 
before the contents of the young individual were again liberated as 
a zoospore. The plant, resulting on the latter’s germination, was still 
less developed, until in the final stage the zoospore on coming to rest 
merely surrounded itself with a membrane, and after some hours, 
without further germination, the contents were again set free. Such 
are the last struggles for the maintenance of the species against the 
accumulating masses of bacteria ! 
Under normal conditions the zoospores of Oed. capillare on coming 
to rest formed a well-developed basal disc, and after a short time 
proceeded to divide and form a two-celled plant (Fig. 23, /). 
Poulsen 1 has carefully described this first division in the case of an 
(unluckily) unknown species. He found that this first division took 
place in a manner rather different from that found in the adult plant. 
He says (loc. cit., p. 5): ‘When the club-shaped cell prepares to 
divide, the first preparation for the stretching (of the cell) is made by 
part of the cell-membrane’s inner layer, which lies in the uppermost 
arched part (and thus has the form of a spherical cap), thickening 
itself, so that this layer, consisting of pure cellulose, is at least double 
as thick as usual at the point mentioned. However, it is thickened 
far more strongly at its lower end than higher up in the arch.’ In the 
fully developed condition this is not unlike the normal cellulose-ring 
in appearance, ‘ but there is the difference, that whilst the ring’s 2 . . . 
outline . . . makes acute angles with the cell-membrane’s inner limit, 
there is only one of these angles present here, . . . namely, the lower 
one ; above the ring goes slowly over into the upper, less thickened 
part of the cellulose layer (cf. Figs. 7, 8, 13, 12).’ In the next stage 
of development a hemispherical slit appears in this thickened portion 
of the wall, and stretches down into its swollen lower margin, dividing 
this part of the membrane into two (secondary) layers. 4 When the 
thickened part of the cellulose-layer has reached its ultimate develop- 
ment, the upper end of the wall of the cell is burst off as a little 
1 Botanisk Tidsskrift, 3rd ser., vol. ii, 1877-79, p. 1, &c. 
8 The ring in the cell of the adult plant is meant here. 
