46 THE COLOURS OF FLOWERS. 



flowers with usually irregular corollas, which represent 

 of course a higher stage of development in adaptation 

 to insect visits. 



Of these, three good illustrative cases are included 

 in the British flora. They are the Polygalacece, the 

 Violacece, and the PapilionacecB. 



Polygala vulgaris^ or milkwort, our only British 

 representative of the first named family, is an ex- 

 tremely irregular flower, very minutely and remark- 

 ably modified for special insect fertilisation. It is 

 usually a bright blue in colour, but it often reverts to 

 pink, and not infrequently cv^en to white. Two of 

 the sepals are coloured, as well as the petals. 



The ViolacecB or violets are a whole family of 

 bilateral flowers, highly adapted to fertilisation by 

 insects ; and as a rule they are a deep blue in colour. 

 This is the case with four of our British species, Viola 

 odorata, V. canmay V. hirta, and V. palustris. Here, 

 too, however, white varieties easily arise by reversion ; 

 while one member of the group, the common pansy, 

 V. tricolor, is perhaps the most variable flower in all 

 nature. This case, again, will receive further attention 

 when we come to consider the subject of variegation 

 and of reversion or retrogression. 



The P apilionacece or peaflowers are closely related 

 to the roses, but differ conspicuously in their bilateral 

 form. The lower and smaller species, such as the 

 medick, lotus, and lady's fingers, are usually yellow, 

 though often reddish outside. So also are broom 

 and gorse. Among the more specialised clovers, 

 some of which are fertilised by bees alone, white, 

 red, and purple predominate. Even with the smaller 

 and earlier types, the most developed species, like 



