382 



AUTOGAMY. 



L 



of insect visitors. To obviate this possibility the flower-stalk bends in a gentle 

 curve to one side so as to bring the last-mentioned stigmas into the line of descent 

 of the pollen when it falls from the anthers at the end of the flowering-period. 

 The process in the Ranunculacese referred to only differs from that just described 

 in trifling respects. In Adonis vernalis no outward inflection of the style can 

 take place on account of its shortness, but on the other hand the stamens nearest 

 to the ovaries curve inwards and deposit their pollen upon the adjacent stigmas. 

 In Anemone alpina the anthers of the innermost whorl of stamens are the first to 

 open, and the order of develop>ment is from that whorl outwards. Owing, however, 

 to the fact that the styles are crowded close together in a dense tuft at that earliest 

 stage, autogamy is not effected at once; later on the styles become bent and twisted, 

 and some of the stigmas touch the anthei-s in consequence; and when in addition 

 the pedicel undergoes inflection and causes the flower to nod, the rest of the stigmas 

 are brought vertically under the anthers and catch the pollen which falls fi'om 

 them. In Pyrola unijiora (see fig. 308 ^), a native of fir-woods, autogamy is 

 brought about at the close of the flower's period of bloom by means of a marvellous 

 co-operation of the stamen-filaments and the flower-stalks. The bud about to open 

 (see fig. 308 ') and the young flower whose petals have just expanded (see figs. 

 308 - and 308 ^) are borne on stalks which are strongly curved, and they are thus 

 inverted and pendent. The style is vertical, with the stigma pointing downwards. 

 The filaments are S-shaped and hold the anthers, which are of the pepper-castor 

 type, with the two pores invariably uppermost so that the pollen does not fall out 

 of itself or at anj^ rate cannot come upon the stigma (fig. 308 ^). Insects approach- 

 ing from below brush first against the stigma and directly afterwards against the 

 anthers which are in consequence upset, and besprinkle the intruders with pollen. 

 This pollen is then carried to other flowers of Pyrola uniflora, where it is retained 

 by the viscid stigmas and fertilizes the ovules. During the period of bloom two 

 changes are effected, which though not very striking in themselves are yet of 

 extreme importance with a view to autogamy. In the last stage of the flower 

 the curve of the pedicel no longer amounts to a semicircle, and consequently the 

 flower is no longer absolutely pendulous but only facing obliquely down (fig. 308*); 

 the style is no longer vertical, but with this new position of the fiower points also 

 obliquely downwards and the stigma is thus brought underneath some of the 

 anthers. The filaments are still curved in the shape of the letter S but in the 

 opposite direction to that held by them at the commencement of the flowering- 

 period (c/. figs. 308 ^ and 308 ^) ; the anthers are therefore inverted and have their 

 pores directed downwards. The least shaking of the slender stem by the wind is 

 now sufficient to cause a fall of pollen, and, in its present position, the viscid 

 stigma cannot fail to get sprinkled with some particles from the shower which 

 descends on such occasions (see figs. 308 * and 308 ^). 



In Phygelius capensis, a plant belonging to the Scrophulariacere of the Cape, 

 and also cultivated elsewhere in gardens for the sake of its deep scarlet flowers, the 

 branches of the inflorescence and the pedicels stand out nearly horizontally from 



