THE BIRTHWORT FAMILY 



127 



28. The Birthwort Family 



(Aristolochiaceae). 



■4 



Climbers. Leaves alternate, exstipulate. Flowers regular or zygo- 

 morphic, perianth tubular, anthers six, sessile, inserted round the base 

 of the stigma. Ovary inferior, of six carpels. Placenta parietal. Seeds 

 endospermous. 



The Indian Birthwort (Aristolochia indica). 



(Plate Xo. 241.) 

 {Kan. Isvara-beru. Mai. Perumarunnu. Taw. Isuraver. San. Ahigandha.) 



This is a smooth climber, growing in the thicket of jungles. 

 The leaves are variable in shape: linear, ovate, or obovate- 

 oblong, and have rounded or auricled bases, and their petioles 

 serve as tendrils in support of the winding stem. 



The flowers that rise in the axils 

 in small racemes exhibit a peculiar 

 structure. The dark green perianth 

 is tubular, forming a globular cavity 

 at its base and a brown tongue at its 

 upper end. If we split the tube open, 

 we find in the kettle-like cavity the 

 broad end of the pistil crowned with 

 a six-lobed stigma. Round the base of 

 the stigma there are six sessile anth ers. 

 In fresh flowers we' And bristles in 

 the narrow floral tube pointing down- 

 wards to the cavity. 



Such a peculiar flower can be 

 pollinated only in a peculiar manner. 

 Small midges attracted by the smell 

 of the flower enter into the cavity. 

 If they come from other (older) flow- 

 ers, they bring pollen with them and 



brush it against the stigma, which in Aristolochia ripens before 

 the stamens. The juicy walls of the prison in which the insects 

 are caught give them nourishment. After about two days the 

 stigma shrinks, but the anthers at the base of it open and let 



Fig. 1 17. — Longitudinal section 



of flower of Arislolochia. 



1. Before pollination, 



2. after pollination. 



