ANTHOCYANINS AND GENETICS 147 



We may now consider the ranges of variation in greater detail. 

 The simplest series is that which involves variation to albinism only, 

 and, in the case of some genera grown as horticultural plants, this is 

 the only important colour- variation known : the type produces antho- 

 cyanin, and the albino is without that pigment. As examples we may 

 quote : Datura Stramonium (Thorn-apple), Dictamnus Fraxinella (Rue), 

 Geranium sanguineum, Epilobium angustifolium, Lavatera trimestris, 

 Linaria Cymbalaria, Malope trifida, Malva moschata and Polemonium 

 caeruleum (Jacob's Ladder); in some of these species there may also 

 be different intensities of type colour due to heterozygous forms (see 

 p. 183). 



If it should happen that the type produces both anthocyanin and 

 plastid pigment, then loss of anthocyanin will not give a white variety but 

 a yellow. Examples of such a case are the yellow varieties of Abutilon 

 spp., Fritillaria imperialis and the variety lutea of Atropa Belladonna; 

 in all these species the type is yellow suffused with anthocyanin. 



Variation to redness, in addition to variation to albinism, is charac- 

 teristic of another series. Variation to redness is a more complex 

 phenomenon than albinism, and the series requires analysis. In the 

 first place the type may be one of two kinds ; it may be either some shade 

 of magenta, purple, or purplish-red, or it may be blue. As examples 

 of the first group we may suggest Anemone Pulsatilla which has a variety 

 rubra; Clarkia elegans (Bateson, 524) which has a red (pink) variety, 

 the type being magenta. Linaria alpina (Saunders, 586) and Pisum 

 sativum (Garden Pea) (Lock, 518) have definite red varieties; Salvia 

 Horminum (Saunders, 487) is violet in type with a red variety, and of 

 Viola odorata there is a variety redder than the type. With the 

 exception of the last, all the above mentioned also give true albinos. 

 Examples of the second group (type blue) are Centaurea Cyanus (Corn- 

 flower) of which purplish-red and pink varieties are known; Lobelia 

 Erinus and Vinca minor (Periwinkle) produce a purplish-red variety 

 and Myosotis sylvatica (Forget-me-not) a pink; Delphinium Ajacis 

 (Larkspur) and Campanula medium have both mauve and pink varieties ; 

 in Aquilegia vulgaris (Columbine) the type is violet-blue, and there are 

 several purplish-red and pink varieties. This second group also varies 

 to white, though it is doubtful in some cases whether there is complete 

 albinism. In other species there is more than one grade of variation 

 to redness. In the garden Stock (Matthiola) (Saunders, 487) it is believed 

 that the type was some shade of purple; there is a crimson (blue-red) 

 variety and also a true red, ' Terra-cotta.' Of Dianthus barbatus (Sweet 



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