

34 MB. H. C. BOBBY OX THE COLOURING-MATTEBS OF 



On the Characteristic Colouring-matters of the Red Groups of 

 Alg*e. By H. C. Sorby, E.R.S., F.L.S., Pres. R.M.S., &c. 



[Bead May 6, 1875.] 



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In my paper " On Comparative Vegetal Chromatology "* I showed 

 that the three great divisions of Alga? — the olive, the red, and the 

 green — are, on the whole, very definitely distinguished from one 

 another by the presence or absence of the various green or yellow 

 substances insoluble in water belonging to the chlorophyl and 

 xanthophyl groups. I now propose to consider more especially 



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the general distribution of some of the principal coloured consti- 

 tuents which are soluble in water. It would be difficult to find 

 another series of colouring-matters of greater beauty, or with 

 such remarkable and instructive chemical and physical pecu- 

 liarities. 



Although all easily soluble in water, there seems very good evi- 

 dence to prove that in the living plants they are either in a solid 

 state or combined with a very small quantity of water, and not 

 disseminated through the whole liquid contents of the cells, like 

 the entirely different class of red colouring-matters found in the 

 leaves of the higher classes of plants. On keeping the Algae in a 

 small quantity of water, they soon die and begin to decompose ; 

 and then the various colouring-matters are set free and dissolved, 

 the change being indicated by the absorption-band in the spec- 

 trum being a little nearer the blue end than in the spectrum 

 of the living plant, and by the fluorescence being greatly in- 

 creased. In some Algae this change takes place very rapidly, and 

 in some so slowly that the colouring-matters are lost by decom- 

 position before a satisfactory solution can be procured ; but by 

 using no more water than is necessary to cover the plant operated 

 on in a small corked bottle, a solution may generally be obtained 

 which is of beautiful pink or purple colour, according to the 

 nature of the plant. Such a solution, after having been filtered, 

 must be carefully studied by the same spectrum method as I have 

 described in many previous papers, and by the employment of 

 special means which I now propose to explain. 



The total number of different coloured substances character- 

 istic of the various divisions of the red groups of Algae is at least 

 six. These are distributed in very variable proportions in different 



* Proc. Boy. Soc. vol. xxi. p. 142. 



