RELAPSE AND RETROGRESSION. 73 



still of tliat colour, and only deepening into blue as 

 the flower opens. Hence individual reversion is here 

 almost universal as an occasional incident in every 

 species. The columbine {Aquilegia vulgaris) is blue 

 or dull purple, sometimes red or white. The larkspur 

 {^Delphinium ajacis) often declines from blue to pink 

 or white. The monkshood {Aconitum napellus) is an 

 extremely deep blue, very rarely white. White violets 

 everybody knows well. The rampions (P/iytcuma) 

 vary from blue to white ; so do many of the cam- 

 panulas. Gentiana campestris is sometimes white. In 

 most Boraginecs — for example, in borage, viper's bu- 

 gloss, and forget-me-not — pink and white varieties arc 

 common. Pink and white Veronicas also occur in 

 abundance among normally blue species. Prunella 

 vulgaris occasionally produces rosy or white blossoms. 

 White wild hyacinths are often gathered. Many 

 other cases will suggest themselves to every practical 

 botanist. 



Blue flowers, however, very seldom revert to yellow, 

 though this change takes place in some cultivated 

 hyacinths, and somewhat differently in the pansy. As 

 a rule, the blue goes back only as far as those shades 

 from which it has more recently been developed. 

 This is, perhaps, the true rationale of De Candollc's 

 law of xanthic and cyanic types. 



Sometimes, indeec, wo may say that the new colour 

 has not yet begun to fix itself in the species, b^t that 

 the hue still varies under our very eyes. Of this the 

 little milkwort {Polygala vulgaris) affords an excel- 

 lent example, for it is occasionally white, usually pink, 

 and frequently blue. Here we may fairly regard 

 the pink as the normal hue, while the white is doubt- 



