478 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



extent in all their organs, and it is equally true of many other plants, the 

 statement is not of universal application. There are numerous plants in 

 whose flowers anthocyan is certainly localised and bound to morphological 

 units. 



Crocus clirysanthus furnishes an example similar to that of the Prim- 

 rose. S. Arnott, writing of this species, says that the typical flower is of 

 a uniform rich orange colour. White, sulphur-yellow, and lilac varieties 

 are known, as well as others which have the outer segments suffused with 

 rich brown, or feathered with brown.* The brown colour is no doubt a 

 combined colour due to anthocyan and a yellow xantheic pigment. 



On the flowers of Faba vulgaris there are small dark brown markings 

 which are due to a dissolved pigment in the cell-sap of the epidermal 

 cells. This appears to be truly brown, not a yellow pigment in large 

 quantity. Neither concentrated sulphuric acid nor solution of potash 

 gives any colour reaction with it. 



Combined Colour Effects of Pigments. 



The commonest instance of the production of such combined effects 

 is that due to the admixture in the same cell of blue and red anthocyan. 

 x The undissociated molecule of anthocyan is blue, the dissociated ion is red. 

 Where in slightly acid cell-sap there are undissociated and dissociated 

 anthocyan, the colour effect is due to a mixture of blue and red. 



Mention has been made of anthocyan and xantheic pigment in solu- 

 tion together. Such instances are very rare, but are to be met with in 

 Antirrhinums, some Iceland Poppies, and in some Roses. The colour 

 effect varies from a reddish-brown to a flushed yellow. Many yellow 

 Rose petals take on this flushed colour in drying. 



Differently coloured pigments, closely contiguous to each other, pro- 

 duce a combined colour effect. The peculiar lurid colour of some garden 

 varieties of Delphinium is due to their mosaic structure. Epidermal cells 

 of the corolla, lying side by side with each other, contain some red and 

 others blue anthocyan. These plants are said to be of hybrid origin, 

 amongst their parents being the scarlet D. nudicaule and the blue 

 D. cashmerianum. Slightly flushed Primroses have epidermal cells 

 containing rose-coloured anthocyan side by side with others containing 

 yellow xantheic pigment. Both colours, however, are so unsaturated in 

 this case that only a very washed-out effect is produced. 



It has already been pointed out that when a portion of a pigment 

 separates from solution in the cell the light absorption is largely increased. 

 When, as is the case with some of the xantheic pigments, the separated 

 solid pigment is of a different hue from its solution, not only is the 

 absorption increased, but its character is altered. Instances of this occur 

 in Ctelogync cristata, C. ocellata, Verbascum nigrum, and some others. 



But most frequently combined colour effects are produced by anthocyan 

 in one of its many hues overlying chloroplastids or chromoplastids. The 

 effect varies with the concentration and hue of the anthocyan, the hue and 

 number of the plastids, and the distance which separates the two 

 pigments. 



* Gardeners' Chronicle, March 11, 1905, p. 14 . 



