CH. Il] CHLOROPHYLL. 53 



used. In the last-named the red colour can be obtained 

 by boiling a leaf in water, which takes out the coloured 

 cell sap, and leaves the leaf green. In the case oi Ricinus 

 the red colour is destroyed by boiling. If these leaves are 

 partly immersed in boiling water, the parts which have 

 been heated reveal, almost at once, the chlorophyll. The 

 red colour may be restored to the fluid in which the leaf 

 has been heated, and also to the leaf itself by acid. The 

 explanation of the facts given by Molisch^ is that as soon 

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

 makes the anthocyan alkaline, when it is greenish or nearly 

 colourless. According to the same author the leaves, e.g. 

 those of Amaranthus, which do not lose their red colour 

 on being boiled, contain an acid cell sap which is not 

 entirely neutralised by the alkaline protoplasm, and there- 

 fore 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 Polysvphonia it 

 is not destroyed. 



(64) Broiun sea-tueeds. 



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 whole of the colouring matters. 



1 Botan. Zeitung, 1889, p. 20. 



