76 THE COLOURS OF FLOWERS. 



And in the fourth place, white varieties of blue iElowers 

 usually have the centre bluish and the edge white; 

 pink varieties have the centre bluish and the edge 

 pink, and so forth. Here, we know what the normal 

 colour is like, and can see that the new hue appears 

 first at the periphery. For example, white violets, 

 a variety of Viola odorata, have the spur and lower 

 part of the petals blue or bluish ; the whiteness only 

 extends to the broad part of the petals. In a large 

 number of varieties examined by the writer, the same 

 law holds good. Hence we are justified to some 

 extent in assuming that when a plant exhibits a 

 different colour at the base and at the tip of the 

 petal, the basal colour is probably more primitive 

 than the peripheral one. 



If we turn from the white violet, with its blue spur, 

 to the very variegated pansy, we may perhaps ask 

 ourselves which is the earlier of its colours, the purple, 

 the white, or the yellow. But if we observe that the 

 spur, unseen at the back of the flower, is usually deep 

 violet blue, as are also the bases of the petals, while 

 the yellow is usually found on the most expanded 

 and modified part of the corolla, the lowest petal, and 

 in its xHost nodal or functionally attractive part, just 

 in front of the honey-cavity, we can hardly resist the 

 inference t^" ''ustupon us by analogy — that the pansy was 

 once all blue, and that the yellow has been developed 

 here, as in the snapdragon and the ivy-linaria, to guide 

 the bees to the proper place for securing the nectar 

 and effecting cross fertilisation. 



It is an interesting fact in this connection that an 

 immense number of the very simplest flowers, when 

 not themsel/es yellow, have yellow spots or patches 



