COLOURS OF FLOWEES. 395 



and may in some cases be traced to the existence of tannin, gallic acid, 

 and iron. Blue flowers, under the process of desiccation, are often 

 ■whitened. Ipomcea Learii, in drying, changes from blue to red. 



Remarkable changes take place in the colour of some flowers 

 during the course of the day. The flowers of the common pink 

 Phlox, early in the morning, have a lightish blue colour, which alters 

 as the sun advances, and becomes bright pink. (Enothera tetraflora 

 has white flowers which change to red. Hibiscus variabilis has its 

 flowers white in the morning, pink at noon, and bright red at sunset. 

 The colour of many flowers of Boraginacese, before expansion, are red ; 

 after expansion, blue. The bracts of Hakea Victoria are yellowish- 

 white in the centre the first year ; the second year, what was white 

 becomes a rich golden yellow ; the third year, the yellow becomes rich 

 orange ; the fourth year, the colour becomes blood-red ; the green 

 portion of the bracts becomes annually darker. It has been stated 

 that soils have an effect on the colour of flowers. The flower of the 

 common Hydrangea hortensis may be changed from pink and rose- 

 coloured to blue, by growing the plant in certain kinds of loam and 

 peat earth. Alum in the soil is said to produce a similar effect. 



Kohler and Schubler have endeavoured to determine the relative 

 proportions between the different colours met with in flowers. They 

 examined upwards of 4000 species, belonging to twenty-seven natural 

 orders, of which twenty were dicotyledonous and seven monocotyle- 

 donous. The following are some of their conclusions : — 



The proportion of white, cyanic, and xanthic flowers varies in 

 different quarters of the globe, and at different eleyations. The follow- 

 ing are the proportions of colour in different natural orders, deduced 

 from the examination of about 120 species of each : — 



Eed. Violet. Blue. Green. Tel. Orange, White. 



Thus, Nymphseaceae and Eosacese, according to Schubler and Kohler's 

 observations, contain a large number of white flowering species; Primu- 



