548 TRANSACTIONS AND PROCEEDINGS OF THE [Sess. lx. 



associated with some modification of the chlorophyll., 

 Again, both the Phaophycese and the Cyanophycepe have 

 associated with their chlorophyll both a lipoehrome and 

 another pigment soluble in water. Phycophaein, the 

 pigment of the former, is of a brownish colour, while 

 phycocyan, that of the latter, forms a beautifully blue 

 solution with red fluorescence. 



The only other pigments which need to be mentioned 

 here are the soluble yellows, which are liable to be con- 

 fused with the lipochromes. The rind of the lemon, the 

 florets of the dahlia, and some other plant tissues, contain 

 yellow colouring-matters, soluble in both hot and cold 

 water, which do not give the lipoehrome reactions ; of their 

 chemistry little is known. 



In concluding this discussion of the common pigments of 

 plants, it seems not out of place to consider the bearing of 

 the facts mentioned upon current theories as to the origin 

 of colour. In spite of criticism from various quarters, it is 

 still the custom to regard the colours of fruits and flowers 

 as entirely the result of the selective action of other 

 organisms. The colours of these structures are, as we have 

 seen, generally speaking, due to lipochromes or to anthocyan 

 pigments, or to a combination of the two. Xow we know 

 nothing of the origin of the lipochromes, it may be that 

 they are simply the outward expression of a well-nourished 

 condition of the organism ; but the colours of autumnal 

 leaves, and of the variegated leaves of cultivated plants, 

 show that the predominance of the lipoehrome pigments is 

 simply evidence of diminishing powers of assimilation. It 

 is, therefore, eminently natural that these pigments should 

 become increasingly prominent, as the parts of the flower, 

 including the carpellary leaves, diverge more and more from 

 the leaf type, and become increasingly incapable of assimila- 

 tion. (For an essentially similar line of argument, see a 

 paper by Mr. Philip Sewell (17).) This fact of observation 

 is quite independent of theories such as that of Simroth, 

 which assume that the lipochromes are directly produced 

 by the alteration of chlorophyll. Again, the anthocyans 

 arise in certain conditions from tannins, which tend to 

 occur naturally in parts of the plant which are growing 

 actively or assimilating feebly. Thus we see that the 



