THE STEMS AND FOLIAGE OF PLANTS. 39 



these and many others always look fresh and green 

 during the very hottest months. 



There is yet another plant which must be mentioned, 

 and that is the Aloe,. There are many kinds in Africa. 

 They have thick, massive, sharp-pointed leaves a yard 

 or more in length, forming a huge rosette. If one cuts 

 a leaf across, it will be seen to be full of a soft mass 

 abounding in fluid. This is water held in reserve, while 

 special vessels contain a resinous substance, which, 

 when boiled down, the drug called " bitter aloes " is 

 made out of it. 



Now, in Mexico similar plants grow, in just the 

 same kind of places, dry and rocky, and they are called 

 " American Aloes," but when the flowers are in blossom 

 they prove to be of quite a different family ; so just as 

 the Mexican Cac'tus resembles the South African Euphor- 

 hlas, so the Aga'vc, as it is called, resembles the Aloe of 

 Africa, showing that quite different plants can put on 

 precisely the same forms, when growing in similar 

 climates, because those forms are best suited for them 

 under the circumstances. 



A substance often secreted on the surface of plants 

 in dry countries is wax. It forms the " bloom " on 

 grapes and plums, and on the Cape '' Wax-berry ; " but 

 on the surface of leaves it helps to prevent the loss of 

 water. Dr. Marloth, of Cape Town, thus describes a 

 very remarkable instance. The plant is known as 

 Sarcocau'lon, a word meaning "fleshy stem." He says 



