CH. Il] CHLOROPHYLL. 53 



used. In the last-named the acid anthocyan can be ex- 

 tracted by boiling a leaf in water, which takes up the 

 coloured cell sap, and becomes red. The leaves of the 

 red variety of Ricinus turn green on being heated, but 

 the red colour does not appear in the water used for the 

 purpose. Both the leaves and the water in which they 

 were boiled may be reddened by treatment with acid. 

 The explanation of the facts given by Molisch 1 is that as 

 soon as the leaf is killed, the strong alkalinity of the 

 protoplasm makes the anthocyan alkaline, when it ac- 

 quires a yellow or greenish tint. According to the same 

 author the leaves, e.g. those of Amaranthus, which do 

 yield a red solution on being boiled, contain an acid cell 

 sap which is not entirely neutralised by the alkaline 

 protoplasm, and therefore preserves the red colour of the 

 anthocyan. 



(63) Floridece. 



In some species, at any rate, the colouring matter 

 reddens cold fresh water in which the sea- weeds are placed, 

 but the colour is destroyed by boiling. In Polysiphonia 

 it is not destroyed. 



(64) Brown sea-weeds. 



A portion of Fucus or Laminaria yields a brown colour 

 to water in which it is boiled while the boiled thallus 

 shows a greenish colour and yields a green alcoholic 

 extract. But it is impossible as far as we have seen to 

 extract the Avhole of the colouring matters. 



1 Botan. Zeitung. 1889, p. 20. 



