1887-88.] Colouring Matters of Leaves and Flowers. 281 



green and four yellow. The green contained nitrogen and 

 a variable amount of carl)on, from 66 to 72 per cent. ; the 

 yellow were destitute of nitrogen, containing from 66 to 71 

 per cent, of carbon, and the colours of the yellow series 

 varied from pale yellow to yellowish-brown. The fact of 

 the existence of such a definite series of colours so closely 

 related, which, as Sachsse shows, differ from one another 

 chemically, without having distinct spectra, may point to an 

 alteration continually taking place in the constitution of the 

 chlorophyll. It is not necessary to suppose that these 

 substances were all produced as a result of the dissolving 

 out of the chlorophyll. 



Is it not a feasible supposition, that just as we now 

 recognise etiolin as a step in the formation of chlorophyll, 

 and xanthophyll as a step in its decomposition, so we may 

 regard the individuals of these series determined by Sachsse 

 as other steps still more close to one another ? AVe may 

 thus perhaps come to regard the condition of the chlorophyll 

 in the plant as really analagous to the condition of the pro- 

 toplasm from which it is derived ; for just as there is now 

 recognised in protoplasm a continually ascending and de- 

 scending series of albuminoids, so we may recognise in the 

 green colouring matter, with its distinct spectrum, a series of 

 more or less stable compounds ever increasing and decreasing 

 in complexity. These, under varying conditions, may be 

 expected to alter in their relative proportion to one another 

 in the cells of the plant, and may account for the varying 

 composition of chlorophyll according to the many differ- 

 ent analysts who have given us the results of theii- 

 researches. 



Pure chlorophyll has never been obtained, although many 

 have supposed for a time that they had extracted it for 

 analysis. Gautier and Hoppe-Seyler obtained by evaporation 

 green crystals of a substance which they termed chlorophyllan, 

 because of the ash present ; for this Gautier suggests the 

 formula 0^31122^203. 



Wollheim in 1887 deduced a formula for pure chloro- 

 phyll, agreeing with Tschirsch's formula for phyllocyanin, 



^'28H47^^3^6- 



The following is a comparison of percentage compositions 

 as given by them : — 



