464 TROPICAL NATURE 



way caused the pollen to stick to some part of its body, 

 which was always the exact part which the insect, on visiting 

 another flower, would bring in contact with the stigma, and 

 thus fertilise it. These investigations explained a host of 

 curious facts which had hitherto been facts only without 

 meaning, such as the twisting of the ovary in most of our 

 wild orchids, which was found to be often necessary to bring 

 the flower into a proper position for fertilisation, the exist- 

 ence of sacs, cups, or spurs, the latter often of enormous 

 length, but shown to be each adapted to the structure of 

 some particular insect, and often serving to prevent other 

 insects from reaching the nectar which they might rob with- 

 out fertilising the flower, the form, size, position, rugosities, 

 or colour of the lip, serving as a landing-place for insects and 

 a 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 it 

 became evident that every peculiarity of these wonderful 

 plants, in form or structure, in colour or marking, in the 

 smoothness, rugosity, or hairiness of parts of the flower, in 

 their times of opening, their movements, or their odours, had 

 every one of them a purpose, and were, in some way or other, 

 adapted to secure the fertilisation of the flower and the pre- 

 servation of the species. 



Researches on the Cowslip, Primrose, and Loosestrife 

 The next set of observations, on some of our commonest 

 English flowers of apparently simple structure, were not less 

 original and instructive. The cowslip (Primula veris) has 

 two kinds of flowers in nearly equal proportions : in the one 

 the stamens are long and the style short, and in the other the 

 reverse, so that in the one the stamens are visible at the 

 mouth of the tube of the flower, in the other the stigma 

 occupies the same place, while the stamens are half-way down 

 the tube. This fact had been known to botanists for seventy 

 years, but had been classed as a case of mere variability, and 

 therefore considered to be of no importance. In 1860 Darwin 

 set to work to find out what it meant, since, according to his 

 views, a definite variation like this must have a purpose. 



