THE FLOWER. 2 1 



brilliant in deserts, at high altitudes on mountains where 

 the sunlight is strong and continued, and also in the far 

 north as at Spitzbergen (Ekstam). It is probable that 

 the colours, white, pink, red, blue, and purple, involve 

 successively greater expense of material. Blue-purple 

 will probably require the greatest amount of sunlight- 

 energy, and white or yellow the least. It is also known 

 that the coloured flowers of a species give off more 

 water in transpiration than the white, and that petals 

 will lose three or four times the amount of water that a 

 leaf does in the same time. The peculiar glossy sheen 

 of Pansies, Gloxinias, etc., is produced by the surface 

 of the petal cells being raised up into little rounded 

 mirrors. The play of light upon these produces the 

 sheen. 



So also with scent, which is generally used in 

 flowers for exactly the same reason as colour. The 

 esters or scents are probably due to the action of free 

 acids on alcohols. They are, in the case of Otto of 

 Roses, produced in the epidermal cells of both surfaces 

 of the petals. Mountain air produces a finer and more 

 delicate fragrance, and the scent is strongest when the 

 flower is just opening about 9 a.m. Perfumes form a 

 considerable industry, and the products are very 

 valuable. A kilogramme of Otto of Roses is worth 

 from ;^2 8 to ;^32 ; but this quantity would require for 

 its production from two to three acres of Roses. The 

 flowers of wild garlic are said to have a faint hyacinth 

 perfume to attract insects, whilst the leaves have a 

 most disagreeable odour to keep off browsing animals. 



However colour and scent originally developed, 

 whether by the sun scorching some individual flowers red 

 in the way in which one often 'finds the leaves and stems 

 of plants in sunny places red and discoloured, or by 



