ORIGIN OF ORGANIC COLOUR. 
267 
if the velocity only is enhanced, the wave-lengths will be shortened ; 
if the velocity and amplitude are both increased, the effect upon the 
wave-lengths will depend upon the proportionate increase of each of 
these factors. 
In which of these forms the concentrated energy will be stored 
must depend upon the special molecular structure of each individual 
organism, or of the species to which it belongs. Some forms of 
molecular structure will probably not admit of increased amplitude 
in the vibrations. In these the concentrated energy will go to 
enhance the velocity, and the wave-lengths will be shortened ; in 
other forms there may be less resistance to increase of amplitude, 
and the waves will be lengthened. It will thus be seen that the 
organic phenomenon connected with food assimilation may alter 
the molecular motions, and so produce changes in the absorption of 
light, and consequently in the colour of the objects. 
But why should these changes be always in the direction of 
unification ? 
Pursuing the previous line of argument, it must be evident that 
although accumulating energy may increase both the amplitude 
and the velocity of the molecular vibrations, there must in all cases 
be a limit to such increase. When any molecules have reached 
that limit of possible increase their power of absorbing ceases, and 
light waves falling upon them which would previously have been 
absorbed must now be reflected. 
As long as the energy of the organism continues to accumulate, 
the number of molecules whose absorbing power is thus exhausted 
will increase, and the quantity of reflected light will increase 
correspondingly. It is noticeable that in plants the formation of 
blossom is always coincident with more or less arrest of growth. If 
the energy which would have been expended in growth is at this 
time concentrated in the molecular structure, the absorbing power 
of a large number of molecules is likely to be filled up, the amount 
of reflected light will be increased, and the flowers which represent 
the arrested growth, and therefore would probably contain the 
non-absorbing molecules, will appear brilliantly lighted, and with a 
December, 1893. 
