40 THE HISTOLOGICAL DISTRIBUTION [CH. 



Another class of combinations is the outcome of the mixture of 

 anthocyanin and a soluble yellow pigment in the same cell. Such a 

 combination occurs in the crimson flowers of Mirabilis Jalapa, though, 

 on the whole, it is usually found to be characteristic of varieties which 

 have arisen under cultivation, as for instance in the crimson varieties 

 of Antirrhinum majus, Dahlia variabilis and Portulaca grandiflora. In 

 these species the flower of the original wild type had some shade of 

 magenta anthocyanin only. Three variations are then characteristic- 

 variation to ivory-white, to yellow and to crimson, the latter being a 

 mixture of magenta anthocyanin and soluble yellow pigment, such a 

 combination as would not normally occur in nature. 



It is interesting to note that colour of type and variation in 

 the anthocyanin-soluble-yellow series is reversed in the antho- 

 cyanin-plastid series. In the latter, the original type is either 

 crimson (Zinnia), yellow striped with brown (Cheiranthus), or orange- 

 red (Tropaeolum) ; a variety characteristic of this series is one in which 

 the yellow pigment almost disappears from the plastids, or is replaced 

 by a much paler yellow substance. When anthocyanin is present 

 with these pale yellow pigments, or the yellow pigment is altogether 

 absent, a purple or magenta variety results, as in the purple Cheiranfhus 

 and magenta Zinnia. When the anthocyanin is more red, as in the 

 orange-red Tropaeolum majus, a carmine variety arises when these 

 pale plastids only are present. Thus, in the anthocyanin-soluble-yellow 

 series we have a magenta (or purple) type with crimson, ivory-white 

 and yellow varieties, whereas in the anthocyanin-plastid series we have 

 a crimson type, with magenta (or purple), ivory and yellow varieties. 



Bidgood (18) mentions one or two unusual colour combinations: 

 the lurid colour of some Delphiniums he attributes to the presence of 

 cells containing red anthocyanin side by side with cells containing blue. 

 Crocus aureus, also, on the outer side of the perianth leaves, shows 

 green stripes which are due to a combination of blue sap colour on the 

 outer side of the perianth leaves and yellow soluble pigment on the 

 inner side. Dennert (14) gives many examples of the different ways 

 in which plastid and sap pigments occur arranged in the tissues, and 

 reference should be made to his paper if details are required. Generally 

 speaking, the anthocyanin pigments occur in the epidermis of the corolla, 

 and the chromoplastid either in the inner tissues, or in the epidermal, 

 or both, and the great variety of such combinations accounts to a large 

 extent for the numerous shades and tints. Dennert also observed that 

 when both plastid and soluble pigments occur in the same cell, 



