JAMES BURTON ON ALGAE COLLECTED IN 1911. 439 



picked up and brought away as an example, and a walking-stick 

 which was stirred in the water looked exactly as though it had 

 been painted. The plant in this case is an exceedingly small 

 spherical body measuring about 3 /x in diameter. It is pale 

 green, becoming blue-green on drying. These multiply by repeated 

 division in all directions, and ultimately form families or colonies 

 of the most various shapes and size. In this particular species 

 they are mostly small and remain solid, though sometimes when 

 older become indefinite in outline and torn. It belongs to the 

 blue-green Algae, and is low down in the scale even for them. 

 The colonies are often aggregated in large masses, the shape 

 to a great extent depending on the prevailing conditions. It 

 occurred in a similar way to that described in the Serpentine 

 a few years ago, and the small waves set up by the wind 

 rolled it into masses more or less globose, and into sausage- 

 shaped bodies often measuring 2 to 4 in. in length. It is 

 called Microcystis marginata. A member of the Club during last 

 summer brought me a tube of it for identification, in which the 

 colonies were of quite typical form as far as can be in such a 

 case. The species is quite common in some of the ponds in 

 Kichmond Park. Perhaps the most interesting record is one that 

 Dr. Cooke calls Clathrocystis aeruginosa (Kiitz), but Prof. West 

 puts it in the same genus as the example I have been speaking 

 of, and calls it Microcystis aeruginosa. I came across it in the 

 small lake in the Zoological Gardens at Clifton, Bristol, early in 

 September last. It was plentiful in all parts of the water at 

 all depths, but on the side to which it was blown by the wind 

 it was as thick as porridge. It was impossible to dip it out 

 with a bottle, it became a pasty and useless mass at once ; one 

 had to fill the tube at some part where it was less dense. As 

 usual under the circumstances, the unlucky waterfowl were 

 having a bad time, and looked green and draggled. The units 

 forming the colonies scarcely differed from those already described, 

 measuring 3 to 4 /x, but they show a tendency to form large open 



