260 TAKING UP OF POLLEN BY INSECTS. 



the Orange Free State. The victims include Plusia precationis, P. Gamma, and 

 ^ P. ehrysitis, Picris BrassiccB, Deilaphila Euphorbice, &c. 



This clamping of pollinia to the feet of insects is quite unique amongst 

 phenomena of the kind observed in the whole realm of plants, and it would be 

 scarcely surprising if people who have not seen the operation with their own eyes 

 were to look upon it as the offspring of a botanist's imagination. There are, 

 however, in the same category, four other cases of behaviour equally calculated to 

 excite astonishment in the observer, and these are all the more remarkable from 

 the fact that in them the transference of pollen to the bodies of insects is effected 

 by means of special movements of different parts of the flower. The insects do not 

 dust off the pollen by coming into immediate contact with it, but their entrance 

 into a flower causes certain changes in the position of the various parts resulting 

 in the pollen being sprinkled, thrown, or rubbed upon particular parts of the 

 intruder's body. 



I do not like comparing these contrivances in plants to the devices of human 

 ingenuity; but the analogy existing between the various kinds of mechanism which 

 effect the transfer of pollen and machines, invented by man, is so close that it 

 would be affectation to refuse to take advantage of the fact that the action of these 

 contrivances in plants can be rendered much more easily intelligible by describing 

 them in terms which plainly indicate their resemblance to simple appliances in 

 use in every household. We shall, therefore, differentiate the various kinds of 

 mechanism for loading insects with pollen, which still remain to be discus.sed, into 

 those provided with piston-apparatus; hammers, or percussive apparatus; springs, or 

 explosive apparatus; and sprinklers. 

 V To begin with, let us take the piston-apparatus in Papilionacefe. In very 



many though not all PapilionaceiB the two lateral petals, called alw or wings, con- 

 verge towards their upper margins, along which they are in contact, so that they 

 form a convex saddle arching over the keel. This arrangement may be seen, for 

 instance, in Coronilla, the Horse-shoe Vetch {Hippocrepis), the Lupine (Lupinus), 

 the Rest-harrow (Ononis), Anthyllis, and in the Bird's-foot Trefoil (Lotus cornicu- 

 latus; see figs. 270' and 270^), the last being the species here selected for illus- 

 tration. The wings are connected with the keel in a peculiar manner. Near the 

 base of each wing is a projecting fold which exactly fits into a socket in the 

 corresponding half of the keel (see figs. 270 ^ and 270 *). Thus wings and keel are 

 locked together, and every pressure upon the pair of alse is transmitted to the 

 keel. Consequently when a hive- or humble-bee sets itself astride on the saddle- 

 ridge formed by the wings, not only is the latter pressed down, but also the 

 keel; and this movement is accompanied, to the astonishment of the observer, by 

 the extrusion of a pasty vermicular mass of pollen through a small opening at the 

 conical apex of the keel, and by the simultaneous adhesion of the pollen to the 

 insect's belly, or sometimes to its legs. The process of expulsion is shown in 

 fio-s. 270 ^■''■'' where a number of stamens lying close together are seen to be 

 thickened into clubs at the part just below the anthers. This bundle of stamens 



