168 BRITISH PLANTS 
All flowers were once pollinated by wind; they were 
small, green, and inconspicuous. This method, however, 
entailed tremendous waste of material, and with it all 
seed-production was uncertain, since pollination was left - 
to chance. When wind, as an agent of pollination, began 
to be replaced by insects, waste was diminished, and seed- 
formation became more certain. Provided it possessed 
adequate material to serve as food for insects, any flower 
which happened to be a little more conspicuous than its 
fellows by certain traits of form or colour, or which 
betrayed its presence to them by some pervading scent, 
was bound to receive greater attention. Insects would 
visit it in greater number, and the production of seed 
would become greater and more certain. Now, this 
would be a distinct benefit to the plant, and plants so 
equipped would be better fitted than others to survive 
in the struggle for existence. This is what has actually 
happened. Every advance made by the flower in the 
direction of making it more attractive to insects has been 
a gain. It has given its possessor an advantage over its 
competitors which, being less efficient, have been gradually 
but inevitably ousted from their habitats. 
As plants have specialized in these directions, the 
pollinating insects have specialized too. Their mechanism 
of flight has been modified for rapid and easy movement 
from flower to flower. They have acquired more skilful 
means of attachment, and the organs by which they 
extract honey have developed into wonderful instru- 
ments of precision. As the corolla-tube became longer, 
and the honey more and more concealed, their tongues 
have become longer and more specialized. The evolution 
of the insect has kept pace with the increasing specializa- 
tion of the flower and the increasing difficulty in obtaining 
honey. 
Entomophilous flowers offer two kinds of food to their 
insect-visitors, and they may be divided into two classes, 
according to the nature of the food which they offer— 
1. Pollen-Flowers, which contain no honey, and are 
visited by insects for the sake of the pollen alone. The 
anthers are large and generally numerous, and the quantity 
of pollen formed is very great. The pollen is taken home by 
bees, and kneaded into a kind of pollen-bread for the grubs. 
Pollen-flowers include the rose, clematis, peony, marsh- 
