268 
ORIGIN OF ORGANIC COLOUR. 
predominant colour according as the special molecular structure of 
that species permitted of the short, the medium, or the long wave 
vibrations being first filled up by the accumulating energy. 
To the same cause may be attributed the green colour of foliage. 
If the energy is concentrated most readily in the vibrations which 
produce waves of medium length, the absorbing power of these will 
be first exhausted, and green light will be reflected. 
The plumule of a germinating seed is generally whitish, indi¬ 
cating a very small amount of absorption. It may be supposed 
that the intense concentration of energy in a seed carries all 
molecular vibration to its extreme limits, and thus prevents the 
absorption of light ; that growth sets free some of this energy, and 
permits absorption of the longer and shorter light waves, thus 
causing the plant to become green ; and that the further expen¬ 
diture of energy is balanced by food which the green plant obtains 
from without, thus preventing any further change until arrest of 
growth causes another decrease of absorption and produces coloured 
flowers. 
Another noticeable fact is that coloured flowers were probably not 
known in earlier geological epochs. In the forests of Calamites 
and Lepidodendrons there was an ample development of the stem 
and branch system, but little foliage, and the prevailing colour was 
probably a gloomy green. In the age of Conifers there was more 
foliage, and the green would be somewhat more pronounced. In 
the Tertiary period, when broad-leafed trees were abundant, the 
forests would have a brighter tint, but it is probable that not 
until the Pleistocene epoch did coloured blossom become character¬ 
istic of the higher plants, the increasing energy of the great organic 
wave not having previously exhausted the absorbing powers of the 
longer or shorter vibrations. 
In the animal world brilliant colour is still comparatively rare, 
this branch of the organic wave being perhaps less advanced than 
that which rules the department of vegetation. In this latter 
department the most brilliant display of coloured blossom is found 
not in trees or shrubs but in herbaceous plants; and this may be 
December, 1893. 
