JAMES BURTON ON ALGAE COLLECTED IN 1911. 437 



were rare, while the coils of the plant were very much longer 

 than in the other case, often reaching ten to fifteen or more 

 turns. A singular fact in both cases was that it seemed impos- 

 sible to concentrate the organism by using the collecting -net ; 

 this was of no consequence, however, as it was so abundant that 

 a dip with a tube secured plenty. I could not find a des- 

 cription of any species that corresponded to this in either of 

 Dr. Cooke's books, or in West's British Freshwater Algae. The 

 nearest seemed to be ^4. circinalis, and under that name a notice 

 of it appeared it Knowledge ; but the form is not circinate, when 

 undamaged, but spiral. It is as though the filaments were 

 wrapped round a cylinder. Hassall (published 1845), however, 

 has a figure very small and not very distinct which appears 

 to represent it ; he calls it Spirillum Thompsoni, but gives as a 

 synonym Anahaena spiralis (Thompson). The habitat is given ds 

 Ballydrain Lake, near Belfast, and there is a description by 

 Thompson of its occurring in great quantity there. He says : 

 *' The specimens obtained were invariably of similar breadth, and 

 rarely presented more than four spiral turns ; and when of this 

 size were ^V^^ ^^ ^^ inch, in length." Further on he refers to 

 its " exact spiral form," but there is no adequate description for 

 identification. The measurement seems to me wrong (I made 

 it out very much smaller : ~^^ to yyVo ^^) '> ^^ magnification 

 is not given with the figure. Why it should be omitted from 

 Dr. Cooke's book, if he had come across it, it is difticult to say ; 

 for the form is so very characteristic and so different from most 

 Anabaenae, though agreeing perfectly in other respects, that one 

 would have thought it could not be overlooked. Prof. West's 

 book does not deal with more than the common species, but 

 describes genera exhaustively. 



Another example of the blue-green Algae which presents 

 several interesting features is Aj)hanizomenon Jlos-aquae. I had 

 not come across it till last year ; but it is recorded as occurring 

 annually in great abundance in the large piece of water known 



