IVc's^ : Phytoplankton of English Lake District. 121 



and Cocconema ventricosum were the most noticeable. Large 

 numbers of small Desmids were present, of which Cosmarium 

 ahhreviatum var. planctonicum was the most abundant, although 

 Staurastrum denticulatum and bi- and tri-radiate forms of St. 

 jacidifemm were exceedingly common. Peridiniiim Willei was 

 frequent, and a few specimens of Anurcea cochlearis were ob- 

 ser\'ed. 



11. Ullswater, Westmorland. May 1903 and September 

 1906. Altit. 476 feet. About 7J miles long by three-quarters 

 of a mile broad. Average depth 83 feet ; maximum depth 205 

 feet. This is one of the larger lakes, mostly with rocky shores, 

 and its upper end is situated among high mountains. The 

 water is somewhat contaminated by the hamlets of Patterdale 

 and Glenridding, and also by the water running from the Green- 

 side Lead Mines. As a result of this slight contamination, the 

 plankton is great in bulk, but poor in quality for the size and 

 situation of the lake. It is an Asterionella-plankton both in 

 May and September. In May little else exists besides the enor- 

 mous quantity of Asterionella formosa, only a few specimens of 

 Tahellaria flocculosa and Dinohryon cylindricum var. diver gens 

 being observed. In September the great mass of Asterionella 

 has amongst it a sprinkling of other Diatoms, a lew Desmids, and 

 a considerable quantity of Dinohryon cylindricum var. divergens. 

 Tahellaria flocculosa occurs in long chains and Tahellaria 

 fenestrata var. asterionelloides is frequent. The Desmids are 

 chiefly Spondylosium pulchriim var. planum, Staurastrum 

 brevispinum (large variety), and St. cuspidatum var. maximum. 

 Oocystis lacustris and SphcBrocystis Schroeteri, both of which are 

 typical plankton-species of the Protococcoideae, were not un- 

 common. AnurcBa cochlearis was also present. 



12. Hawes Water, Westmorland. September 1906. Altit. 

 694 feet. About two and a half miles long by about three- 

 eighths of a mile broad. It is rather an isolated lake, with a 

 maximum depth of 103 feet, and an average depth of about 

 40 feet. The September plankton was somewhat mixed, but 

 was mostly a Diatom-plankton, with a large admixture of Coelos- 

 phcerium Kiitzingianum. The Diatoms were chiefly zig-zag 

 chains of Tahellaria fenestrata, Cocconema gracile, C. cymhiforme, 

 and Synedra Acus. Ceratium hirundinella was common, and 

 sterile filaments of Mougeotia elegantula were frequent. A few 

 Desmids were observed, amongst which Staurastrum jaculiferum 

 was the most abundant. Others were St. denticulatum, Arthro- 



1909 March i. 



