SSO 



AUTOGAMY. 



twofold : the jaws of the flower are set wide open and the honey-secreting lobe 

 hitherto concealed in the hollow of the lip is brought out so as to enable the insect 

 which has caused the movement to lick up the honey without difficulty. In doing 

 so, however, it rubs its back against the stigma, and should it have previously 

 visited older flowers cross -pollination ensues. These are the conditions at the 

 commencement of flowering. The next day or the day after that, the anthers 

 open by comparatively large pores, one at the top of each loculus. The connectives 



are articulated to the fila- 

 ments, so that when the latter 

 are pushed the anthers are 

 set swinging and let fall some 

 of their mealy pollen. If 

 under these circumstances a 

 rather large Hymenopter 

 alights on a flower in quest 

 of honey, he must necessarily 

 knock against the filaments 

 and be sprinkled by the pol- 

 len which descends in conse- 

 quence, especially seeing that 

 the filaments have meanwhile 

 increased in lengfth suffi- 

 ciently to bring the upper 

 lobes of the anthers upon the 

 highest part of the arched 

 external surface of the under- 

 lip. If the flower is not 

 visited by insects, a quantity 

 of the mealy pollen falls of 

 itself upon this convex sur- 

 face (see fig. 307 2). go^n 

 afterwards the flower- stalk 

 curves down, causing a steep 

 inclination of the roof of the under-lip, which still bears on its highest part the 

 heap of pollen deposited by the anthers. The pollen slips down the inclined plane, 

 and is thus brought into contact with the stigma, which still retains its receptive 

 power (see fig. 307^). 



The acccomplishment of autogamy, by means of a combination of movements 

 and inflections of the flower-stalks with similar action on the part of the stamens 

 and style is of as common occurrence as it is varied in respect of details. The 

 drooping Star of Bethlehem (Ornithogalum nutans) derives its name nutans 

 from the attitude of its flowers, but the latter really do not assume that position 

 until quite at the last; in the bud-stage they are erect, and even after the leaves 



Fig. 307.— Autogamy caused by inflection of the flower-stalk and the adjust- 

 ment of the under lip to form an inclined plane down which the pollen 

 deposited upon the under-lip slides to the stigma : Calceolaria Pavonii. 



', 2, 3 Side view of the flower in the three successive stages leading to auto- 

 gamy. ■* Longitudinal section through a flower in the first stage of de- 

 velopment. All the flgs. slightly magnified. 



