334 CHAPTERS ON EVOLUTION. 



depressed with the wings, while the pistil and stamens are thus 

 partly uncovered." In the bean, when the wings are similarly 

 pressed down, the stigma of the pistil, and then the "beard" of 

 the style, laden with pollen, project from the keel, which is of 

 coiled conformation. When a bee exercises the necessary pressure, 

 the pistil of the bean will first strike its body and become fertilised 

 by fresh pollen, whilst the pollen-laden style of the flower will, 

 secondly, leave fertilising matter on the bee's body for application to 

 the pistil of another flower. 



A dead-nettle (Fig. 230), with its irregular flower, presents a favour- 

 able and readily understood example of the manner in which a special 

 form of flower is adapted for the special insect which cross-fertilises 

 it. A bank of dead-nettles is to humblebees what a country-fair is 

 to juveniles, in that it presents the insects with a store of sweets spe- 

 cially intended for their delectation. In shape, the sage (Fig. 235), 

 or dead-nettle flower, as everyone knows, exhibits a wide mouth, 

 bounded by a very much arched upper lip, whilst a divided lower lip 

 is also conspicuous enough. The green cup-like calyx has its sepals 

 united, whilst the very irregularly shaped corolla is composed of united 

 petals. There are four stamens two long and two short the fifth 

 stamen of botanical expectation being abortive. The stamens are 

 peculiar in position, inasmuch as they lie along the arch of the petals 

 (Fig. 230, st\ instead of surrounding the pistil. The style is very 

 long, and forked at its tip (sg), and it moreover depends below the 

 anthers as in fuchsia (Fig. 233). The honey for which the bees visit 

 the dead-nettle is situated far down within the flower, and if we make 

 a vertical section of the corolla, we shall find a circle of hairs (Fig. 

 230, ti) placed inside the petals at their lower portion. Now, in 

 what special fashion is the mechanism, thus described, brought into 

 play in the fertilisation of the dead-nettle tribe ? The reply may 

 be found in a simple study of a dead-nettle on a warm summer's day, 

 when insect-life and the blossoming of flowers together seem to attain 

 the acme of activity and development. The bee approaches the 

 flower, and finds in the lower lip of the blossom a convenient door- 

 mat on which to alight. Here the insect gains a point d'appui for the 

 movement of the proboscis, which probes the depths of the corolla so 

 as to reach the nectar, and easily thrusts aside the circlet of stiff hairs 

 presenting an impassable barrier to a less robust as well as uninvited 

 insect guest. The acts of the insect, in so far as the work of honey- 

 getting is concerned, end thus. Meanwhile, however, it has likewise 

 been performing its unconscious part in the fertilisation of the flower. 

 The position of the stamens under the hooded petal has been noted. 

 Such a position assures two results firstly, that the stamens shall 

 be brought in contact with the bee's body ; and secondly, that the 

 pistil shall likewise touch the insect in order that foreign pollen, 



