THE BOOK OP ROSES. 55 



nature. Orange, as of the nasturtium, admits 

 little variation of shade; and pure yellow is 

 almost invariable in flowers. It may be re- 

 marked in cruciform and composite flowers, 

 and Linnaeus, Lamarck, De Candolle, and other 

 botanists, have not hesitated to accept it as a 

 steady specific character. 



An essay on the colouring of flowers was read 

 before the Academy of Medicine, in Paris, in 

 1824, in which it was asserted, that their various 

 shades of colour were produced by the phy- 

 siological and chemical results of their absorp- 

 tion of gaseous fluids. The author, (Monsieur 

 Lemaire de Lisancourt,) had ascertained by 

 experiment, that the corolla of yellow flowers 

 contains alkali ; that pink, red, or scarlet flowers 

 contain carbonic acid ; while those containing 

 neither acid nor alkali, are uniformly white. 

 From this it may be inferred, that yellow and 

 orange are specific physiological colours ; while 

 red, considered in all its shades of pink, crim- 

 son, scarlet, purple, may also serve to charac- 

 terize a species. It may be objected, that other 

 yellow roses exist besides the simplicifolia, 

 lutea, and sulphurea; but these, instead of 

 being of a pure bright yellow, are greenish, or 

 of a dingy hue, not the result of the presence 

 of alkali. 



The fundamental colour of all vegetable- 

 tissues, is, as chemists have demonstrated, a 



