PDF - Wallace Online

464 TROPICAL NATUREway caused the pollen to stick to some part of its body,which was always the exact part which the insect, on visitinganother flower, would bring in contact with the stigma, andthus fertilise it. These investigations explained a host ofcurious facts which had hitherto been facts only withoutmeaning, such as the twisting of the ovary in most of ourwild orchids, which was found to be often necessary to bringthe flower into a proper position for fertilisation, the existenceof sacs, cups, or spurs, the latter often of enormouslength, but shown to be each adapted to the structure ofsome particular insect, and often serving to prevent otherinsects from reaching the nectar which they might rob withoutfertilising the flower, the form, size, position, rugosities,or colour of the lip, serving as a landing-place for insects anda guide to the nectar-secreting organs, the varied odours,sometimes emitted by day, and sometimes by night only,according as the fertilising insect was diurnal or nocturnal,and other characters too numerous to refer to here, so that itbecame evident that every peculiarity of these wonderfulplants, in form or structure, in colour or marking, in thesmoothness, rugosity, or hairiness of parts of the flower, intheir times of opening, their movements, or their odours, hadevery one of them a purpose, and were, in some way or other,adapted to secure the fertilisation of the flower and the preservationof the species.Researches on the Cowslip, Primrose, and LoosestrifeThe next set of observations, on some of our commonestEnglish flowers of apparently simple structure, were not lessoriginal and instructive. The cowslip (Primula veris) hastwo kinds of flowers in nearly equal proportions: in the onethe stamens are long and the style short, and in the other thereverse, so that in the one the stamens are visible at themouth of the tube of the flower, in the other the stigmaoccupies the same place, while the stamens are half-way downthe tube. This fact had been known to botanists for seventyyears, but had been classed as a case of mere variability, andtherefore considered to be of no importance. In 1860 Darwinset to work to find out what it meant, since, according to hisviews, a definite variation like this must have a purpose.