216 



PHYSIOLOGICAL BOTANY. 



Apocyneie, Artocarpete, &c. They differ very remark- 

 ably in their characters; for although a large portion 

 are noxious, and even highly poisonous, some on the 

 contrary are wholesome and nutritious. There are 

 several substances found in the composition of these 

 milks, of which we may mention the following : 



1. Caoutchouc, or Indian rubber is abundant in 

 some of them, and may be readily obtained from several 

 trees of different families growing in tropical climates. 

 All that is requisite for the purpose of procuring this 

 material, is to receive the milk into suitable vessels as 

 it flows from a wound in the bark and to allow its 

 aqueous particles to evaporate, when the caoutchouc re- 

 mains in a solid form. 



2. Opium is procured by inspissating the milk of 

 the poppy, and is also found in other plants. 



3. The Cow. Tree. One of the most remarkable 

 phenomena of the vegetable world is the cow-tree 

 described by Humboldt in the following terms, as 

 growing in the Cordilleras of South America : " On 

 the barren flank of a rock grows a tree with dry and 

 leather-like leaves ; its large woody roots can scarcely 

 penetrate into the stony soil. For several months in 

 the year not a single shower moistens its foliage. Its 

 branches appear dead and dried ; yet as soon as the 

 trunk is pierced, there flows from it a sweet and nou- 

 rishing milk. It is at sunrise that this vegetable foun- 

 tain is most abundant. The natives are then to be 

 seen hastening from all quarters, furnished with large 

 bowls to receive the milk, which grows yellow and 

 thickens at the surface. Some empty their bowls under 

 the tree, while others carry home the juice to their 

 children. The milk obtained by incisions made in the 

 trunk is glutinous, tolerably thick, free from all acri- 

 mony, and of an agreeable and balmy smell. It was 

 offered to us in the shell of the tutuno, or calabash 

 tree. We drank a considerable quantity of it in the 

 evening, before we went to bed, and very early in the 

 morning, without experiencing the slightest injurious 



