THE MONOPETALOUS ORDERS. 



455 



rolla, opposite leaves, and the whole internal surface of the ovary 

 ovuliferous ! Ex. Obolaria. 



853. Ord, Apocynacea? (the Dogbane Family}. Trees, shrubs, or 

 herbs, with milky juice, and opposite entire leaves, without stipules. 

 Flowers regular. Calyx five-cleft, persistent. Corolla five-lobed, 

 twisted in aestivation. Filaments distinct ; the anthers sometimes 

 slightly connected : pollen granular. Ovaries two, distinct, or 

 rarely united, but their styles or stigmas combined into one : in 

 fruit usually forming two follicles. Seeds often with a coma. 

 Embryo large and straight, in sparing albumen. Ex. Apocynum 

 (Dog's-bane, Fig. 950), Vinca (Periwinkle) ; and a great number 

 of tropical shrubs and trees. In all, the juice is drastic or poison- 

 ous, and often yields caoutchouc ; which in Sumatra is obtained 

 from Urceola elastica. The well known Nux vomica is the seed 

 of Strychnos Nux-vomica of India. S. toxifera yields the famous 

 Woorari poison of Guiana. One kind of Upas is obtained from 

 the bark of the root of S. Tieute in Java. The poisonous princi- 

 ple in these plants is an alkaloid, called Strychnia. 



854. Old, Asclepiadaceffi (the Milkweed Family}. Herbs or shrubs, 

 with milky juice, and opposite entire leaves ; mainly differing from 

 the preceding order (as they do from all other Exogenous plants) 

 by the peculiar connection of the stamens with the stigma, and the 

 cohesion of the pollen into wax-like masses, which are attached in 



FIG. 950. Apocynum androssemi folium. 951. Flower of the natural size. 952. Stamens 

 with the anthers connivent around the pistils. 953. The pistils with their large common 

 stigma. 954. Seed with its coma, or tuft of silky hairs. 



