POLLINATION OF ARISTOLOCHIA. 



793 



of the hairs at the base of the enlargement, which now widens; the flies, 

 having deposited on the stigmatic surface the pollen which they brought with 

 them, can now therefore creep under to the open anthers where the pollen of 

 the latter becomes attached to them. About this time, moreover, the throat r of 

 the flower has also become passable from within ; the trap-like hairs in it having 

 perished and dried up as a result of the pollination of the stigma. The insect, 

 laden with the pollen of this flower, can now escape, and, in spite of its late 

 experience, it again forces its way into a younger flower, there to give up to the 



FIG. ^^o.—Aristolochta Clctiiatitis. Portion of stem st, with 

 petiole *, in the axil of which are flowers of various ajfes. i, i young 

 and as yet unfertilised flowers ; 2.2 flowers which have been fertilised 

 and bent downwards ; k flask-like enlargement of the fluwer-tube r ; 

 ythe inferior ovaries (nat. size). 



Fig. 451. — Aristolochia CUmatttis. Flowers in loH' 

 gitudinal section ; A before, and ß after fertilisation 

 (enlarged— see text). 



still receptive stigma the pollen it has brought with it. While the above changes 

 are going on in the interior of the flower, the latter, moreover, alters its position. 

 So long as the stigma in the young flower is still receptive, the pedicel is erect, 

 and the perianth open outwards (Fig. 450 i, i,), presenting to the flies a hospitably 

 open door; but as soon as they have accomplished the j)ollination of the stigma, 

 the pedicel bends sharply downwards at the base of the ovary, and when the 

 flies, again laden with pollen, have flown away from the flower, the banner-Hke 



