2 INTRODUCTION 
most important work both for themselves and for the plants. Their needed susten- 
ance, little drops of a sweet nectar, is hidden away down in these flowers. It costs 
them some trouble and labour to collect it; and during their manifold movements 
it comes about that they gather pollen in great quantity among the hairs of their 
body, to which it readily adheres, and rub it off again on the stigmas. As the 
surface of these is covered with innumerable warts, tubes, or spines, and smeared 
with an oily moisture, the pollen adheres more readily than to other parts of the 
flower. The insects, moreover, put pollen on the stigmas in a quantity far 
exceeding what is sufficient for complete fertilization; and this they do in so 
many flowers that Nature perfectly achieves her purpose. It will now be under- 
stood how it happens that cucumbers and melons will not prosper in hot-beds 
that are too well covered in. Until now, pollination of the female flowers has 
been ascribed to the wind, but other views would necessarily have prevailed 
if only close attention had been paid to the relative positions of the male and 
female flowers, to their forms, and to the character of the pollen. And how 
can one do this without at once recognizing in these busy insects the true 
agents of pollination? Certainly any one who had made these observations before 
me would have discovered this, and would have cleared up for himself and for all 
other Naturalists this secret of Nature. Whoever will convince himself of the truth 
of what I have here maintained with all caution, should give close attention through- 
out a whole day in still, clear, and warm weather (for then pollination is most 
commonly effected) to all that happens to one of the plants in question. He will 
then see that all manner of insects gradually assemble among the flowers, after 
these begin to open, that they wander about in them, and pass over from one to 
another. He will see that one after the other in the course of its manifold move- 
ments and turnings, gathers, on the hairy parts of its body, sometimes more, 
sometimes less of the pollen hanging on the stamens of a male flower, and soon 
thereafter either passes into another flower of the same kind, or goes into a female 
flower. In this latter case let him not disturb the insect, but await its voluntary 
departure, watching meanwhile at some distance all its movements. When it has 
gone, he should examine with a lens of low power the inner surface of the flower on 
all sides; and then pollen belonging to the same plant, and of which previously 
there was not a trace, will be found here and there adhering to the hairs of the 
flower, and especially to the stigma, which previously was quite free from it. 
This drama may often be seen re-enacted in the same blossom, so that the stigma 
about the time when the flower begins to close, will be almost completely covered 
with pollen. Occasionally, one may notice with satisfaction how a few of the 
insects roll about in the pollen, how they cover their whole body with it, and how, 
in this new golden costume they carry the fertilizing material in bulk to the female 
flowers.’ 
We find here a clear representation of cross-pollination by the help of insects, 
along with information as to the most favourable time for making observations, 
In the course of the memoir referred to, Ké6lreuter describes adaptations for 
pollination in several plants, e.g. in Iris, Malva, and Viscum; he also recognizes 
the dichogamy of Polemonium, Oenothera, and Epilobium. Referring to the flowers 
of the last-named plant (pp. 34 and 35), he says: ‘The flowers of the willow-herb 
