PROCEEDINGS OF SOCIETIES. 71 
(Ralfs) = Peniwm curtum (Bréb.). Mr. Archer had but once 
before seen living specimens, and they were brought by Mr. Crowe 
from Wales. The present specimens occurred in considerable quan- 
tity by the road-side in a little shallow pool—almost a puddle— 
close by the foot-path just before you come to the bridge over the 
Dargle-River on the road between Bray and Enniskerry. This 
very habitat might indicate that this species may be more common 
with us than might at first sight appear; occurring where one 
might almost least expect to find it, and far removed from the 
situations where other Desmidiacee abound, it may be overlooked. 
Alex. Braun, in his ‘Rejuvenescence in Nature’ (p. 203, note), 
adverts at some length to this pretty species, and he blames Ralfs 
for placing it in the genus Cosmarium, remarking that a regard 
to the arrangement of the cell-contents should have saved him 
from the error of placing it in that genus, and not in Penium, to 
which Braun thinks it properly belongs. But if the endochrome 
being arranged in fillets (radiately in end view) should remove 
this plant, notwithstanding its possession of a distinct constric- 
tion dividing the frond into two segments, from Cosmarium to 
Penium, the same reason should hold good as regards Cosmariwm 
Ralfsii, 1 very large and very deeply constricted form. That 
pretty and, with us, rare form, Cosmarium moniliforme, likewise 
shows an arrangement of the endochrome in fillets. However, in 
making these remarks, and in drawing attention to the fact that 
Braun’s reasoning must apply to other forms than COosmariwn 
curtum (Ralfs), Mr. Archer would by no means aver that the dis- 
position of the endochrome in these plants may not be of even 
greater importance than the outward figure, and there can be no 
doubt but that it is at least equally constant and characteristic, 
in its way, of certain species. Thus, the genus Pleurotenium may 
be very good, containing, as it does, forms referable in outward 
figure on the one hand to Cosmarium, and on the other to Doci- 
dium. But, again, characters-drawn from the arrangement of the 
endochrome are under the disadvantage of not being available 
unless the specimens are quite fresh and recent ; in mounted pre- 
parations the cell-contents become so altered that such characters 
mostly become quite irrecognisable. Moreover, if this course were 
fully carried out it would seem almost as if Penium and Closte- 
rium should be united, as the endochrome in both genera is in 
fillets (radiate in end view), a step which Braun and those who 
hold with him do not adopt or sanction. 
Mr. Archer likewise presented specimens of Closteriwm linea 
(Perty), common here, but the peculiarity consisted in the 
numerous examples having become aggregated in greater or less 
numbers into bundles or fascicles, the individuals closely approxi- 
mating and cohering, sometimes juxtaposed side by side into 
long-drawn-out chains, more or less overlapping. ‘The central 
pair of each bundle, closely encompassed by numerous othet 
fronds, had become conjugated, ‘and the subcruciate zygospdre 
