166 



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



[Oct. 30, 



the Jakes of the western British areas stand ahead of any other lakes which 

 have so far been investigated. 



The numerous Scottish lakes are almost all of a montane character. 

 They are situated in the vicinity of high mountains and in a northern 

 latitude, and many of the higher plants occurring in these localities in 

 abundance, at almost sea-level, are typical montane species.* 



The lakes of the four principal areas examined, the North-west Scottish, 

 the West and South-west Irish, the Welsh, and the English lakes, are 

 situated in the most mountainous parts of the British Islands. As these 

 areas contain the great majority of the British lakes, and are all 

 geographically in the west or north-west, they can be spoken of as the 

 western and north-western lake-areas. The mountains amongst which they 

 are situated are composed almost entirely of old formations, and the lake- 

 basins are for the most part drainage areas on outcrops of Older Palaeozoic or 

 of Precambrian rocks, often with associated intrusive Igneous masses. 



Malham Tarn, West Yorkshire, and Lough Neagh are somewhat isolated 

 lakes, and their phytoplankton is considered separately. 



Wherever possible, boats were used for the collection of the plankton, and 

 for one part of the investigation of Lough Neagh, the Lough Foyle and 

 Eiver Bann Fisheries Company kindly lent a steam launch. The smallest 

 tow-net had a mouth-diameter of 6 inches and a length of 15 inches, the 

 largest was 12 inches diameter and about 36 inches in length. The nets 

 were usually towed after the boat at a speed of about 1^ to 2 miles per hour, 

 but on Lough Neagh the large nets were used up to a speed of 4 miles per 

 hour. They were generally kept in the water from 20 to 30 minutes. 



We have come to the conclusion that the best fixing agent is 2 or 3 per cent, 

 formalin, but it should always be replaced before the material is examined. 



Neither picric acid nor chromic acid should be used in plankton-work, as it is 

 almost impossible to wash the material free from these reagents by ordinary 

 methods, and all the gelatinous colonies are broken up. Alcohol is also to be 

 avoided, as it causes too great a shrinkage and distortion of the more delicate 

 plankton species. 



During the past 18 years we have been acquiring a very extensive 

 knowledge of the distribution of British freshwater Algae, having made many 

 thousands of collections in all parts of the British Islands. As the lake- 

 areas are the richest parts of the country for freshwater Algaa, these districts 



* Occurring in abundance around these lakes are : — Festuca ovina, var. vivipara, Andrecea 

 Rothii, A. petrophila, Bryum alpinum, various species of Rhacomitrium, Anthelia julacea, 

 Platysma triste, Cladonia cervicornis, Stereocaulon coralloides, Sphwrop>horon coralloides, 

 Lecidea geographica, etc. The whole district is almost treeless. 



