OF PLANTS. 195 



the strange stalk and toad-coloured, ill-smelling flowers of 

 Stapelia ? But this family is not less interesting in other 

 respects. The best Caoutchouc at present known, that 

 from Pulo Penang, comes from a plant of this family 

 (Cynanchum ovalifolium). Also that from Sumatra, 

 (Urceola elastica, Roxb.), from Madagascar (Vahea gummi- 

 fera, Poir), a part of the Brazilian (Collophora utilis, 

 Mart, and Hancornia speciosa, Mart.), and the East Indian 

 (Willughbeia edulis), are obtained from plants which 

 belong to the group of Apocynacece. 



Most strangely, this family also, as well as the following 

 and last, exhibits the peculiar phenomenon which was 

 described in the first-named, the Euphorbiacete, namely, 

 that the milk-sap is in some species rich in Indian rubber, 

 in others, it is tempered into a clear, agreeably smelling, 

 and wholesome milk, while in certain others, on the con- 

 trary, this fluid grows, step by step, through successively 

 increasing quantity of noxious matter, to a most dreadful 

 poison. In the forests of British Guiana grows a tree 

 which the natives call Hya-Hya (Taberncemontana utilis, 

 Arn.) Its bark and pith are so rich in milk that an only 

 moderate-sized stem -which Arnott and his companions 

 felled on the bank of a large forest-brook, in the course of 

 an hour coloured the water quite white and milky. This 

 milk is perfectly harmless, of a pleasant flavour, and is 

 taken by the savages as a refreshing drink. Still more 

 pleasant must be the taste of the milk of the Ceylon Cow- 

 tree, the Kiriaghuma (Gymneura lactiferum, Rob. Br.) 

 which, according to Burmann's narrative, the Cingalese 

 use exactly as we do milk. 



Dreadful, on the contrary, is the action of the terrible 

 Wourari poison, which the inhabitants of the banks of the 

 Orinoco concoct with mystic conjurations, the chief ingre- 



