ALG^. 



119 



^^^""^I 





nature, and a species of Rivularia. It was after- 

 wards pronounced to be Rivularia ecJiinata. Along 

 with it, but in very small quantity, was Aiiabcena 

 flos-aqiia; (Fig. 23). 



"In the first week of July, 1847, the same species 

 was observed similarly associated, but the Anab(zna 

 was now more plentiful, without any corresponding 



diminution in the quantity of 

 i\\Q Rivularia. In July, 1848, 

 it was observed that the 

 Rivu/aria was as rare as the 

 AnabcBua had been in 1846 ; 

 to the latter, consequently, 

 the water of the loch now 

 owed its colour, which was 

 of a very dull green : the 

 colour, however, becomes 

 brighter when the plant is 

 dried. In neither of the 

 seasons mentioned was it in my power to make any 

 observations on the colour of the loch earlier or later 

 than the date above mentioned, consequently nothing 

 can be added respecting the comparative development 

 and progress of the two plants at other seasons." ^ 



De Candolle has called attention to Lake Morat, 

 in Switzerland, stating that during every spring it 

 presents the appearance of a reddish scum upon its 

 surface, which the fishermen express by saying that 

 the lake is "in flower." In 1825 the phenomenon 

 continued from the month of November until May, 

 and its unusual exuberance was supposed to originate 

 * Annals and Magazine of Natural History, January, 1849, p. 21. 



o 

 O 



"1 



Fig. 23. — Anahaua Jtos-aqua. 



