360 



AUTOGAMY. 



branches below the sweeping-hairs, and may be recognized by the granulated 

 appearance of its turgescent cells. The behaviour of the stylar branches from the 

 commencement to the termination of a flower's bloom is shown in fig. 302 \ where 

 the three tubular florets are in successive stages of development. Almost simul- 

 taneously with the opening of the tubular corolla the two style-branches are pushed 

 up above the anther-tube, and the pollen is swept out of the tube by the hairs pre- 

 viously referred to. The style-branches at this period are in close contact, and the 

 receptive tissue of the stigmas is not yet accessible (fig. 302 \ left-hand floret). 



Autogamy by means of a crossing or a bending back of the style-branches. 



■ Aster alpiims. Portion of a capituliini, incluJing a marginal female floret with ligulate corolla and three tubular florets of 

 the disc. The latter are in the successive st,iges which lead to autogamy (left to right). = Style-branches of Aster alpinus 

 which have just separated but still have some pollen clinging to their hairs, a The style-brimches crossed so as to transfer 

 the pollen from the collecting-hairs of the one to the stigmatic tissue of the other. *, s, « Florets from tlie centre of a 

 capituluni of Centaurca monlana in successive stages leading to autogamy. ' The two style-branches rolled ijaclv sulB- 

 ciently to bring the stigmatic tissue into contact with the pollen ou the collecting-hairs. » Campamda persicifotia; 

 longitudiiial section through a newly-opened flower. ' The same with the style-brauches rolled back so as to bring the 

 stigmatic tissue into contact with the pollen ou the exterior surface of the stylar column. " Flower of Phyleuma orbimUre 

 in process of transition from the lirst to the second stage of development. " The same flower in the last stage of develop- 

 ment. 8, 9 natural size ; the rest magnilied. 



Neither cross- nor self-fertilization of the flower in question can at present be 

 eiiected, and the pollen is only exposed that it may be carried away by insects to 

 fertilize other blossoms. The two style-liranches are subsequently lifted still 

 higher and move a little apart, with tlie result that the pollen clinging to their 

 hairs, if not already removed by insects, is for the most part pushed otf, falls down, 

 and is appropriated to the purpose of geitonogamy (see p. 321). A small remnant of 

 pollen is, however, invariably left hanging to the lower collecting-hairs, and this it 



