42 THE COLOURS OF FLOWERS. 



in the species, for one may often find a night lychnis 

 at the present time which is only pale pink, instead of 

 being pure white. 



Sir John Lubbock remarks of the CaryophyllacecB 

 that " the order presents us with an interesting series 

 commencing with open-flowered species, the honey of 

 which is accessible even to beetles, and short-tongued 

 flies, through those which are adapted to certain flies 

 (Rhingia) and Bees ; to the species of Dianthus, 

 Saponariay and Lychnis Githago, the honey of which 

 is accessible to Lepidoptera only." It is a curious 

 fact that in just the same progression the flowers pass 

 gradually from small white inconspicuous petals to 

 large and deeply coloured red or purple ones. 



The Cistacece are another family of simple flowers, 

 with the carpels united, but otherwise very primitive 

 in form. Their petals usually spread around the ovary 

 in a regular discoid form ; and the earliest members 

 only differ essentially from Potentilla in the union of 

 their carpels into a single imperfectly three-celled 

 capsule. Our English genus, Helianthemuni or rock- 

 rose, comprises some of the smallest and simplest 

 forms, with yellow petals, and very like Potentilla in 

 general appearance. One species, however, H.poli- 

 folium (a mere slight variation on the yellow H. 

 vtilgare), has white flowers. The larger South Euro- 

 pean forms, which make up the genus Cistus, have 

 much more expanded petals, and these are usually 

 white, pinkish, or rose-coloured. One Mediterranean 

 species has a yellow centre with white edges : another 

 closely allied to it, has a white centre with pink edges. 

 Here, as in the roses, mere increase in size (coupled 

 of course with special insect selection) seems to have 



