438 JAMES BURTON ON ALGAE COLLECTED IN 1911. 



as the " pond " near the Palm-house in Kew Gardens. On 

 August 28th the water was suffused with it at all depths. It 

 consists of short filaments of cylindrical cells about 4 to 5 /a wide,, 

 the divisions slightly constricted ; a heterocyst with clear con- 

 tents is usually present. The filaments adhere to each other- 

 in numbers, forming flakes or scale-like objects of considerable- 

 size, easily visible to the naked eye. The protoplasm is bluish 

 green with darker granules. A fortnight later the plant had 

 increased in amount, till on the lee side it formed a thick pasty 

 mass, which the waterfowl avoided. It produces spores, long and 

 somewhat thicker than the filament, but there were very few on 

 the first date, and later, when there were more, it was evident- 

 that the organism was breaking up, and from that time it 

 gradually disappeared. It cannot usually be found in this- 

 water at any time. It has been stated that with it is generally 

 found another organism, Clathrocystis, but I found none ; on the 

 occasion when the Aphanizomenon was first seen, there was 

 present with it in almost equal amount the beautiful Eiidwina 

 elegans. This is most likely better known than the other ; it 

 is of considerable size, and from its elegant shape and graceful, 

 motion is not unlike the closely related Volvox globatoi\ It belongs 

 to the Chlorophyceae the green Algae and is a much higher 

 organism than Aphanizomenon. I have not read or heard of its 

 occurring in such abundance, and it had entirely disappeared 

 on the second visit a fortnight later. 



A well marked example of the " breaking of the meres " on 

 a large scale happened in the summer of 1911 at the Brent 

 Keservoir. On August 31st the whole of the water of one division 

 of the lake was of a distinct pale green ; near the edge on the 

 lee side the appearance was most remarkable. The water re- 

 sembled green oil or thin paint ; it was being drawn off, and in 

 consequence the bank for some distance from the edge, and the 

 various debris and rubbish left on the bank, were covered with 

 a thick deposit of the organism. I have a small stone which was 



