80 THE COLOURS OF FLOWERS. 



/, fulva is orange, dappled with deep brown. Both 

 are almost certainly products of retrogressive 

 selection. 



Something of the same sort is seen in Cheiranthus 

 cheiri, the wallflower. This large and highly de- 

 veloped stock-like crucifer is a peculiar yellowish 

 brown in the wild state, frequently even primrose or 

 primitive yellow. But it varies readily, often be- 

 coming red at the edges ; and under cultivation it 

 assumes numerous shades of red, purple, and brown. 

 It appears to be a product of retrogressive selection 

 from an original form like the European stock. This 

 flower, combined with some others like Adonis 

 autumnalis, Ranunculus Ficaria, and Lotus corniculatus, 

 seems to suggest the idea that yellow may sometimes 

 merge directly into red, without passing through the 

 intermediate stages of white and pink. The other order 

 would appear, however, to be the more regular and 

 usual gradation. 



In the Primulacece, we find similar instances. 

 Hottonia palustris, a less developed form, is rosy 

 lilac. Cyclamen europaum is white or rose-coloured. 

 Trientalis europcea is white or pale pink, wjth a yellow 

 ring. From such a stage as this, it is easy to get at 

 our primroses, cowslips, and oxlips, which have pale 

 yellow corollas, with orange spots at the throat. 

 Indeed, one English species, Primula farinosa, is 

 pale-lilac, with a yellow centre : and this might easily, 

 under special circumstances, become pale primrose all 

 over. The cultivated varieties of the cowslip, called 

 Polyanthuses, readily assume various tints of orange, 

 red, and pink, always at the edge, the deep yellow 

 of the throat remaining unchanged. On the other 



