122 IVes/ : PhytoplauMon of English Lake District, 



desmus crassus, Spondyloshim pulchrum var. planum, and 

 Gonatozygon monotcBnium var. pilosellum. Anurcea cochlearis 

 was frequent. 



13. Grasmere, Westmorland. June and September 1903. 

 Altit. 208 feet. About a mile long by half a mile broad. It has 

 a somewhat rocky margin, and its greatest depth is 180 feet. 

 The water may be slightly contaminated by the village of Gras- 

 mere. The September plankton was largely a combined Dia- 

 tom and Dinohryon-plankton. The Diatoms consisted almost 

 exclusively of Asterionella formosa and Tahellaria jenestrata var. 

 asterionelloides. The Dinohryon was D. cylindricum var. 

 diver gens. Ceratiiim hirundinella was fairly common, and 

 C. cornutnm and Peridinitim Willei occurred in small quantity. 

 A few Desmids were fairly general, among which Xanthidium 

 suhhastiferum var. Murrayi and Staurastrum cuspidatum var. 

 maximum were the most conspicuous. The most noteworthy 

 Desmids were Cosmarium controversum and Micrasterias 

 M ahabiileshwarensis var. Wallichii, the former being known 

 from North Wales and N.W. Scotland, and the latter only from 

 the plankton of lakes in Sutherland and the Shetland Islands. 

 A sterile species of Mougeotia was frequent, and the filaments 

 exhibited a coiling comparable to that observed in several of 

 the Scottish lakes.* (Fig. i c. and d.). Species of Mougeotia 

 occur in a living condition in the plankton of very many of 

 the British lakes, throughout the greater part of the year, and 

 the coiling of the filaments undoubtedly shows the development 

 of a limnetic character, due to adaptation of the plants to an 

 existence in the plankton. The coiling of the filament very con- 

 siderably increases its floating capacity. 



Several of the Myxophyceae were not uncommon, more par- 

 ticularly Oscillatoria Agardhii, Anahcena Lemmermannii , and 

 Microcystis stagnalis. Two Rhizopods were observed — Arcella 

 vulgaris and a long-spined species of Acanthocystis. 



The June plankton consisted of a mixture of large quan- 

 tities of Dinohryon cylindricum var. divergens and Peridiniitm 

 Willei. Amongst these flagellated organisms were a number of 

 Rotifers, more especially Hydatina and AnnrcBa cochlearis. 



* W. and G. S. West in ' Journ. Linn. Soc. Bot.', XXXV., 1903, p. 

 524 ; also in ' Trans. Roy. Soc. of Edin.', XLI., Part III., 1905, pp. 497 

 and 510. 



[To be continued). 



Maluralist, 



