170 



Mr. W. West and Dr. G. S. West. 



[Oct. 30, 



observations relative to the periodicity of the Scottish phytoplankton are 

 amply confirmed by Bachmann's brief report. 



Desmids are the dominating constituents in the late summer and early 

 autumn, and there is a preponderance of Diatoms in the colder months, but 

 compared with the seasonal variations of the phytoplankton in some lakes, 

 these differences are not very conspicuous. 



Specimens of Dinobryon occur in quantity in the spring and summer, and 

 the Peridinieae are represented by 11 species, although in the larger lakes 

 they are by no means numerous. 



Of a total number of 354 species observed in the phytoplankton, 49 "4 per 

 cent, are Desmidiaceae, 17*7 per cent, are Bacillarieae, and 8*7 per cent, are 

 Myxophyceae. 



III. Lakes of the Orkneys and Shetlands. 



We have examined material from one freshwater loch in the Orkneys and 

 from six in the Shetlands. The collections were made in August, 1903, and 

 the results published in 1905.* Mr. James Murray has collected material 

 from 34 lochs of the Orkneys and Shetlands, and has briefly noted a few 

 species of the phytoplankton.f 



Although containing a considerable number of species, the phytoplankton 

 was not very rich. Most of the lochs were shallow, and contained quantities 

 of Asterionella formosa. Pediastrum Boryanum and Scenedesmus qtuxdricauda 

 were both fairly common. Colonies of a Crucigenia, described by Wille from 

 the Norwegian plankton as C. irregularis^ but most probably only irregularly 

 developed forms of C. rectangularis, occurred in several lochs of the 

 Shetlands. 



Desmids were frequent, and in some cases numerous, but the species were 

 mostly those of shallow lowland lakes. The characteristic western British 

 types were absent, although further investigations in the Shetlands would no 

 doubt bring some of them to light. 



Peridinieae were abundant, as is so frequently the case in shallow lakes, 

 and the ubiquitous Geratium hirundinella was much more generally abundant 

 than in the larger Scottish lakes. 



Out of 52 species of Algae described by Borgesen and Ostenfeld§ as 



* W. and G. S. West, in 'Bot. Soc. Edin. Trans.,' Nov., 1904 [1905], pp. 5—10. 



t James Murray, in ' Boy. Soc. Edin. Broc.,' June, 1905, pp. 55, 56. 



% Wille, in 'Nyt Magazin for Naturvidenskb.,' Bd. 38, Heft 1, 1900, p. 10, t. 1, f. 15. 

 Consult also the remarks of G. S. West, 'Treatise Brit. Freshw. Alg.,' 1904, p. 217 ; and 

 Ostenfeld in 'Hedwigia,' vol. 46, 1907, p. 383. 



§ F. Borgesen and C. H. Ostenfeld, " Ehytoplankton of Lakes in the Faeroes," 1 Botany 

 of the Faeroes,' Copenhagen, 1902. 



