Nov. 1904. | BOTANICAL SOCIETY OF EDINBURGH. 5 
In Roy and Bissett’s “ Scottish Desmidiee” (“ Ann. Scott. 
Nat. Hist.,” 1893-94), the following Desmids are mentioned 
from the Orkneys :—Staurastrum muricatum, Bréb.; Arthro- 
desmus octocornis, Ehrenb., 8 major, Ralis; Cosmarium biocul- 
atum, Bréb.; C. pseudonitidulum, Nordst; Clostervwm uttenu- 
utum, Ehrenb.; Cl. Cynthia, De Not; Cl. intermedium, Ralts ; 
Cl. Leibleinti, Kitz; Cylindrocystis diplospora, Lund ; and Cos- 
marium amenum, Bréb.; Closterium attenuatum, Khrenb.; and 
Penium polymorphum, Perty, from Unst, Shetlands. 
Il.—PHYTOPLANKTON FROM THE ORKNEYS AND SHETLANDS. 
Plankton material was obtained from only one freshwater 
loch in Pomona, Orkneys. This was Loch Kirbister, about 
six miles south-east of Kirkwall, and 49 feet above the sea- 
level. The material was collected on a stormy day, and has 
proved somewhat poor. One of the chief features was the 
presence of numerous specimens of Amphora ovalis, Kiitz, of 
large size. Three typical plankton-species of the genus 
Staurastrum were present, and there were numerous Rhizo- 
pods and Peridiniez. 
On the Mainland of the Shetlands plankton-material was 
collected from Loch Asta (altit. about 26 ft.), Neugles Water 
(altit. 222 ft.), Loch Sandy (altit. about 240 ft.), Loch Trebister 
(altit. 243 ft.), and Loch Brindister (altit. 217 ft.) On Bressay 
material was obtained from several of the Lochs Beosetter 
(altit. about 50 ft.). 
The plankton was not very rich, and this can doubtless be 
partly attributed to the wetness of the season, the lochs being 
very full. Another determining factor of the relative rich- 
ness of the plankton of these lochs was the shallowness of 
the water. They were all small, shallow lochs, and the 
plankton of such bodies of water differs very considerably 
from that of larger rocky lakes, containing fewer species of 
the Desmidiacee. <Asterionella formosa, Hass, was abundant, 
but no specimens of A. gracillima, Heib., were observed, a 
species which is abundant in the plankton of Sutherland, 
Ross, and the Outer Hebrides. 
The most interesting species noticed in the collections were; 
Genicularia Sprrotenia, De Bary, from Loch Beosetter, Bressay 
Closterropsis longissima, Lemm., var. tropicwm, from Loch Asta ; 
