310 



SYSTEMATIC BOTANY. 



sutures ; fruit a pair of follicles, or by abortion 1 ; seeds mostly 

 with a crown of hairs at the hilum, with thin perisperin. 



ILLUSTRATIVE GENERA. 



Suborder 1. PERIPLOCE^:. Pollen granular ; anthers acuminate. Peri- 



ploca, L. 

 Suborder 2. ASCLEPIADEJE. Filaments united into a tube , pollen in waxy 



coherent pollinia. Asdepias, L. ; Hoya, R. Br. j Stapelia, L. 



Fig. 410. 



ct 



\Jf 



o, Flower of Asclepias purpurascens; b, a vertical section, with the petals removed; 

 c, side view of a stamen ; d, inside view of an anther (p, pollen-sac); e, two 

 pollen-masses ; /, cross section of the ovary. 



Affinities, &c. The genera are further grouped into tribes and subtribes, 

 according to the nature of the anthers and pollinia. The curious organiza- 

 tion of the stigma and pollen is the great distinguishing feature of this 

 Order, which in other respects is closely allied to Apocynaceae. When the 

 pollen is mature, it escapes in " pollen-masses " from the anthers (fig. 410, e), 

 and adheres to gelatinous processes developed on the sides of the stigma, 

 which retain it, so that it can push its pollen-tubes into the lateral and 

 inferior stigmatic surfaces ; after fertilization, the stigma with the ad- 

 herent anthers and filaments separate from the style and leave a pair of 

 distinct carpels, which ripen (one or both) into free follicles. 



Distribution. A large Order, mostly tropical, in Asia, Africa, and 

 America; one or two species occur in Europe, and a few in North 

 America. 



Qualities and Uses. Generally resembling the Apocynaceae j but the 

 active properties are not so much developed, and the succulent fruits do 

 not appear here. Species of Asclepias, Cynanchum, Calotropis (Mudar), 

 Tylophora, and Periploca are more or less emetic or purgative ; the leaves 

 of Solenostemma Argliel and Gomphocarpus fruticosus are frequent adulte- 

 rations in Alexandrian Senna, and are said to cause griping. The roots 



