52 



Miss M. Wheldale. Colours and Pigments of [Oct. 31, 



pale form, perhaps an albino, is recessive to the full yellow. He also states 

 that Correns found white Polemonium cceruleum to be dominant to yellow 

 Polemonmm flavum. If the former contained a glucoside-like body, and the 

 latter a xantheic pigment, the result might be analogous to Phlox. As 

 material of these genera was not available, the pigments have not been 

 investigated, and consequently this conjecture must remain unverified for 

 the present. 



Plastid Pigments. 



The plastid pigments, carotin and xanthin, are well-known substances, 

 of which the properties and characteristics have been investigated. Both 

 may be present in the same plastid, when the colour is orange-yellow, 

 orange or orange-red, and this condition is very widely distributed ; or 

 xanthin only may be present, when the colour is yellow. In the orange- 

 yellow or red type the loss of the power to produce carotin in the plant 

 may give rise to a lemon-yellow variety. This is the case in flowers of 

 Argemonc grandiflora, Calendula officinalis, Tagetes signata, Tropmolum 

 majus, and probably Cheiranthus Cheiri and Salpiglossis grandiflora. 



In other cultivated genera, where the type contains xanthin, this pigment 

 appears to give rise to paler yellow varieties containing derivative plastid 

 pigments, probably decomposition products of xanthin, and giving a yellow 

 or brown colour with strong sulphuric acid. At present these derivatives 

 have not been thoroughly examined. They are found in the pale yellow 

 varieties of Hclianthcmum spp., Chrysanthemum carinatum, in the autumn 

 cultivated Chrysanthemum , and in Zinnia elegans. 



There is evidence from cross-breeding in Cheiranthus and Tropceolum* that 

 presence of carotin is dominant to its absence, that is the orange-yellow 

 variety is dominant to the lemon-yellow. 



The plastid pigment in cream varieties of Lathyrus odoratus, MattMola, 

 Rosa, and Eschscholtzia caniculata rosea, is again different from carotin 

 and xanthin as regards its chemical reactions. There is evidence from 

 cross-breeding in Lathyrus and Matthiola (Bateson and Saunders (1)) that 

 cream plastid pigment is recessive to its absence, i.e., colourless plastid. 



Combinations of Soluble and Plastid Pigments. 



Anthocyanin and plastid pigments are frequently found together in plants. 

 When the red sap occurs with plastids containing both carotin and xanthin, 

 the resulting colour is some shade of brown, crimson, or orange-red ; with 

 plastids containing xanthin only, or some derivative product of xanthin the 

 * I am indebted to Miss Saunders for information regarding Tropceolum. 



