452 



Mr. H. C.-Sorby on 



[June 19, 



nature of chlorophyll (I mean of the green constituent of leaves, inde- 

 pendent of the yellow colouring-matters), though, as far as I am aware, 

 no one else has hitherto adopted that opinion. Having said this much, 

 I now proceed to give an account of my own experiments, and of the 

 conclusions which seem to explain the facts in a satisfactory manner. 



Chlorophyll Group. 

 This comprises three perfectly distinct substances, soluble in bisul- 

 phide of carbon and insoluble in water, which agree in having absorption 

 at both ends of the spectrum, in having well-marked absorption-bands at 

 the red end, to the principal of which the strong red fluorescence is 

 related, and in being decomposed with greater or less facility by weak 

 acids into new products, giving somewhat analogous, but yet quite di- 

 stinct spectra to those characteristic of them in their natural state. All 

 are rapidly decomposed in strong sunlight, when air is also present, but 

 not otherwise. 



Blue Chlorophyll. 



I was first led to distinguish the compound nature of the chlorophyll 

 in ordinary green leaves by studying that found in Oscillatorice, as 

 named in former papers. This kind is that which occurs throughout the 

 whole vegetable world, and the difference consists in the usual but not 

 universal presence of another along with it, which second kind differs in 

 the highest and in the very lowest classes of plants. Blue chlorophyll 

 can be best obtained in an approximately pure state from olive Algce, 

 like Fucus or Laminaria, by the method already described. Its spectrum 

 shows three absorption-bands at the red end, that nearest the extreme 

 red being by far the most intense. Unless the solution be very strong, 

 the whole of the green and a considerable portion of the blue are trans- 

 mitted, so that the colour is such a blue-green that the term blue chloro- 

 phyll appears to be very appropriate. Any decided band in the green 

 is proof of the presence of a small quantity of the well-known product 

 of the action of the acids, which very readily decompose it. This change 

 may be avoided by crushing up acid plants with a little bicarbonate of 

 ammonia before dissolviDg the chlorophyll ; but it is far better to make 

 use of those whose juice is more neutral. Mere boiling in water, as 

 adopted by some experimenters, is not sufficient, since the alteration will 

 take place even when the chlorophyll is not in solution. The absorption 

 at the blue end is due to a broad band between the blue and the violet, 

 which can be seen only in a moderately pure solution, with excellent day- 

 light. Besides the product of the action of acids just alluded to, several 

 others can be prepared from blue chlorophyll by decomposing it with acids 

 or alkalies ; but the} r are of little interest in connexion with living plants, 

 except as showing that it is in a state of very unstable equilibrium. 



Yellow Chlorophyll. 

 This substance has not been obtained in a pure state, but yet suffi- 



