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 suflScient 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, Kolreuter 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 



