POLLINATION AND FERTILISATION 27 



advantages (to the flower) of flie different peculiarities presented, 

 especially if he endeavours to confirm his conclusions by direct 

 observations of the nictliods )>y m hicli the pollen cells are distributed 

 to tlie stigmas. 



Pollen cells are usually distributed either by the agency of the 

 wind or by insects ; and it is generally easy to determine, by the 

 nature of the flower itself, which is the method jieculiar to its species. 



A wind- pollinated flower is generally very inconspicuous. It 

 ]n-oduces no nectar, which forms the food of such a large number 

 of insects, and has no gaudy perianth, nor does it emit any odour 

 such as would be likely to attract these winged creatures. It« 

 anthers generally shed an abundance of pollen, to compensate for 

 the enormous loss naturally entailed in the wasteful process of 

 wind-distribution, and the pollen is so loosely attached that it is 

 carried away by the lightest breeze. Further, the anthers are 

 never protected from the wind, l)ut protrude well out of the flower ; 

 and the stigma or stigmas, which are also exposed, have a com- 

 paratively large area of sticky surface, and are often hairy or 

 plumed in siich a manner that they form effectual traps for the 

 capture of the floating pollen cells. 



An insect-pollinated flower, on the other hand, has glands 

 {nectaries) for the production of nectar, and its perianth is usually 

 of such a conspicuous nature that it serves as a signal to attract 

 the insects to the feast. (In some instances the individual flowers 

 are very small, but these are generally produced in such clusters that 

 they become conspicuous through their number.) Often it emits 

 a scent which assists in guiding the insects to their food. Its 

 stamens are generally so well protected by the perianth that the 

 pollen is not likely to be removed except by the insects that enter 

 the flower ; and the supply of pollen is usually not so abundant 

 as in the wind-pollinated species, for the insects, travelhng direct 

 from flower to flower, convey the cells with greater economy. The 

 stigmas, too, are generally smaller, and are situated in such a position 

 that, when mature, they are rul)bed by that portion of the insect's 

 body which is ah-eady dusted with pollen. 



As we watch the nectar-feeding insects at work, we not only 

 observe that the flowers they visit possess the general characters 

 given above as common to the insect-pollinated species, but also that, 

 in many instances, the structure of the flower is such that the transfer 

 of pollen from anthers to stigma could only be accomplished by the 

 particular kind of insect which it feeds. Various contrivances are 



