Closterium acerosum Ehrenb. ex Ralfs

n [ -£$,H “ 5. COSMARIUM ACEROSUM.

CLOSTEEIUH ACmOStJii. (SCHRAKT) EHRB.

(Var. nov. ^¿iSnET*) Fresh-water Algae of the United

States page 18, February 1872. (Smithsonian contribution

to knowledge, £41}*

C. lineare-fusiforme, sub-rectum aut leve curvatum, utroque
fine sensim et paullulum attenuatum, diametro 15-24 plo
longiore; apioibus angustissime truncatis, achrois; mem-
brana haud striata; vesieulis chlorophyllaceia 11-14 in
quoque crure, in serie axilli simplioi collocatis; loeello
apicali parvo, corpuscula numerosa indudente; zygosporis
globosia.

Diam.-Transv. max. 13/7500" = .0017"; zygosp. 20/7500"= .0027".

Syn.—0» acerosum, (SCHRÄNK) EHRB. RABEHHORST, Flora Surop.

Algarum. Sect. 111. p. 128.

Hab.-Pennsylvania; WOOD. South Carolina, Georgia, Florida; Bailey.

Linear, fusiform, straightish, or slightly curved, at each end
sensibly little by little attenuate, 15-24 times longer than
broad; apices narrowly truncate, transparent; membrane not
striate; chlorophyl globules 11-14 in each limb placed in a
simple axillary series; apical vesicle small, containing nu-
merous corpuscles; zygospores globose.

REMARKS.-The desmid, described above, was found in Hew Jersey,
near Camden. It differs from the typical form of C. acerosum
in its size, proportionate length to breadth, and in not being
striate. The European "forma major" (RA32ITH.) appears, however,
to exceed it in transverse diameter, and, according to some
authors, certain fronds of the species are not striate, and all
authorities agree that at times the striae are exceedingly deli-
cate. For these reasons, I think, our American form must be re-
garded simply as a variety. As far as can be judged from the
rude figure, it is this species which Prof. Bailey identifies as
C. Tenue, ETZ., in Silliman’a Journal for 1841.

Fig. 5, and 5 a, pi. 11, represent this species magnified
250 diameters; 5 b represents the sporangium with portions of
the dead fertile fronds still attaohed.

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