THE ORIGW OF FLOWERS. 



155 



become more and more distinctly colored from 

 generation to generation, until they reached their 

 present noticeable form. If we look closely 

 into this matter, we may perhaps be enabled 

 clearly to understand the various steps by which 

 this development of color in flowers was brought 

 about. 



All common leaves contain a green pigment, 

 known to chemists as chlorophyll, from which 

 they derive their ordinary color. The cells of 

 the leaf are stored with this pigment, while their 

 transparent walls give them that superficial sheen 

 which we notice so distinctly in the glossy foli- 

 age of the laurel and the bright fronds of the 

 hart's-tongue fern. But very slight chemical 

 changes in the composition of leaves suffice to 

 give them a different color ; which is not surpris- 

 ing when we recollect that color is nothing more 

 than light, reflected in greater or less proportions 

 of its constituent waves. The fashionable pelar- 

 goniums, coleuses, and begonias, or the dark 

 sedums which are employed to form the quaint 

 carpet-gardens so much in vogue, show us how 

 easily the green coloring-matter can be replaced 

 by various shades of purple, red, and brown. 

 These changes seem on the whole to be connect- 

 ed with some deficient nutrition of the foliage. 1 

 It would appear that the normal and healthy 

 pigment is a rich green ; but that as the leaf 

 fades and dies, it passes through successive stages 

 of orange, pink, and russet. The autumn tints 

 of the forest, the crimson hues of the Virginian 

 creeper, and the transitory colors of a dying 

 plant, all show us these passing nuances. If a 

 single leaf, or even a particular spot upon a 

 leaf, is insufficiently supplied with nutriment, 

 its first symptom of ill-health is a tendency to 

 paleness or jaundiced yellowness. If an insect 

 turns some portion of it into a gall-nut or a 

 blight, the tips assume a beautiful pink hue. In 

 short, any constitutional weakness in the leaf 

 brings about changes in its contained pigments 

 which result in an altered mode of reflecting 

 light. Or, to put the same fact in another way, 

 any change in the composition of the pigments 

 is apt to be accompanied by a change in their 

 color. Now the ends of long branches are natu- 

 rally the least nurtured portions of a plant, and 

 the young leaves formed at such spots have a 

 great tendency to assume a brown or pinky hue. 

 Furthermore, these spots are exactly the places 

 where flowers are formed ; flowers being, as we 



1 1 purposely avoid all reference to the purely tech- 

 nical question of the relation between chlorophyll and 

 erythrophyll. 



saw above, mere collections of aborted leaves, 

 destined to fulfill the function of parents for fu- 

 ture generations at the point where the vigorous 

 growth of the original plant is beginning to fail. 

 Nothing can be more natural, therefore, than 

 that the flower-leaves should show an original 

 tendency to exhibit brilliant hues — a tendency 

 which would of course be strengthened by natu- 

 ral selection if it gave the plant and its descend- 

 ants any superiority over others in the struggle 

 for life. 



It should be remembered, too, that the flower 

 differs from the leaf in the fact that it is not self- 

 supporting. The green portions of a plant are 

 its mouths and stomach : they are perpetually 

 engaged in assimilating from the air and the wa- 

 ter those elements which are fitted for its growth. 

 But the flower is a purely expensive structure : 

 it does not feed itself; it is fed by other portions 

 of the plant. It uses up, in the act of growing 

 and expanding, energies derived from the food 

 which has been stored up by the chlorophyll else- 

 where. Accordingly, we might expect its pig- 

 ment to present that less energetic, more worn- 

 out form, which produces the brighter hues of 

 autumn and the pink tips of a growing bough. 

 From whatever point of view we regard it, we 

 see that a flower is naturally supplied with some 

 coloring-matter less active than that green sub- 

 stance which forms the assimilative agency in 

 common leaves. It is easy, therefore, to guess 

 how certain plants may have acquired the first 

 tinge of color around their organs of fructifica- 

 tion, and thus have attracted the eyes of insects 

 by their superior brilliancy. 



This, however, is only one side of the prob- 

 lem. We can imagine how leaves may have be- 

 come colored to attract insects, but we do not 

 yet see why insects should be attracted by col- 

 ored leaves. Side by side with the development 

 of color in flowers must have gone the develop- 

 ment of a color-sense in insects. The creatures 

 which strayed through the green carboniferous 

 brushwood were doubtless endowed with eyes, 

 sensitive in a considerable degree to light in its 

 varying shades, and to visible form ; but there is 

 little reason to suppose that they were capable 

 of distinguishing between red and blue. We 

 know of nothing in their external circumstances 

 which would have made such a faculty of any 

 value to them ; and we have now learned that 

 every structure presupposes some advantage to 

 be gained by its development. On the other 

 hand, Sir John Lubbock's experiments and ob- 

 servations upon bees leave us little room to doubt 



