Nov.-1904.] BOTANICAL SOCIETY OF EDINBURGH. 19 
Lerwick ; Neugles Water. Plankton of Loch Asta and of Loch 
Beosetter, Bressay. 
. margaritiferum (Turp.), Menegh. “Synops. Desm. in Linnza,” 
1840, p. 219 ; Ralfs, in “ Ann. Nat. Hist.,” 1844, xiv., p. 393, t. 11, 
f. 4. 
be margaritiferum, Ralfs, “ Brit. Desm.,” p, 100, t. 16, f. 2 6 
and d; C. Malinvernianum (Racib.), Schmidie, var. Badense, 
Schmidle in “ Flora,” 1894, t. 7, f. 21.] 
0.—Kirkwall ; Hoy. S.—Scalloway ; Bressay. 
No species of this genus has given rise to greater confusion 
than C. margaritiferum.  Ralfs included three species in his 
figures of it, and the typical form has since received at least 
one new name. The zygospore of true C. margaritiferwm, 
which was well described by both Ralfs and Archer, is globose, 
and its walls are furnished with numerous thickenings which 
have been likened to “ bull’s-eyes.” As the species was under- 
stood by the earlier observers it was undoubtedly common, and 
it possessed this remarkable zygospore. 
Ralfs figures of this plant are not good. He did not 
sufficiently indicate the flattened apices of the semi-cells, nor 
did he figure the minute scrobiculations at the centre and 
between the granules. His figures 2b, 2c, and 2d (on t. xvi.) 
are the only ones which represent the species. 
In 1894 Schmidle described under the name of “ (. Malin- 
vernianum, var. Badense,’ a Cosmariwm which is very abundant 
in the British Islands and in other parts of Europe. It occurs 
principally in bogs, and does not disagree with the published but 
incomplete descriptions of C. margaritiferum. Moreover, it is of 
the same size, and its zygospore, which we have found repeatedly, 
agrees exactly with that described and figured for C. margariti- 
ferum. It is inconceivable that the older investigators could 
have missed such a striking and common Desmid, seeing that 
they repeatedly found most of its associates, and, moreover, 
amongst these associates they invariably recorded “0. 
margaritiferum.” 
Hence, as we constantly find in bogs a Cosmariwm as common 
as C. margaritiferum was reported to be, of the same size, and 
not differing materially from the published descriptions of that 
species ; and as this Cosmariwm occurs with the same associates 
with which C. margaritiferum was generally said to be found, and 
as it has exactly the same zygospore, we are forced to the con- 
clusion that it 7s C. margaritiferwm. 
At the same time the species is unquestionably identical with 
the “ C. Malinvernianum, var. Badense,” described by Schmidle, 
and therefore Schmidle’s name must become a synonym of 
C. margaritiferum. Schmidle was the first to point out the 
constantly flattened apex of the semi-cells and the presence of the 
minute scrobiculations between the depressed central granules. 
We have previously given a figure of the zygospore of this 
species under the erroneous name of “ C. confusum, var. regularius” 
(vide West and G. S. West, in “ Journ. Roy. Micr. Soc.,” 1896, p. 
156, t. 4, f. 41). 
123. CO. Brébissonii, Menegh. S.—Scalloway. 
124. C. trachypleurum, Lund. O.—W. of Kirkwall. §.—Bressay. 
125. C. isthmochondrum, Nordst. 
Var. pergranulatum, var. n. (fig. 20). 
Var. granulis ad margines laterales semicellularum minus 
