THE CACTUS FAMILY. 



391 



ing ridges, furnished with straight or hooked hard spines, apex 

 generally concave, from round the centre of which rise the 

 flowers, being either white, yellow, or crimson, and opening 

 successively for several days during sunshine. 



This group consists of a number of species, varying con- 

 siderably in size, some not exceeding a few inches in diameter 

 and height, and others increasing in size even to 3 feet in 

 diameter and 10 feet in height, the largest being represented 

 by E. visnaga, of which two plants were received at Kew, 

 about twenty-five years ago, from St. Luis Potosi, one 

 measuring 4^ feet in height, and 2f feet in diameter, weigh- 

 ing 713 lb. ; the other 9 feet in height, rather more thaA 

 3 feet in diameter, and weighing about one ton. 



The whole of EchinocactcB are of slow growth, living to a 

 great age, plants being observed to differ little in appear- 

 ance during a period of 24 years. Their substance con- 

 sists entirely of soft fleshy pulp, containing a quantity of 

 water, which is used where water cannot be obtained, their 

 great abundance affording an inexhaustible supply. Mules 

 and other animals break them up and suck them. The 

 Indians also scoop them out and form them into kettles for 

 cooking their food. 



5. Melocactus (Melon Cactae). 



Plants consisting of ridges like Echinocactus, hut differing 

 in its flowers, which are small, being home amongst a thick, 

 compact mass of red-coloured woolly fibres and prickles, vary- 

 ing, according to age, from a few inches to nearly a foot in 

 length, and two or three inches in diameter, forminy a turban- 

 like head. 



The principal species of this group is Melocactus communis, 

 a native of the rocky coast of many of the West Indig, islands, 

 and is well known for its curious head of flowers, called 

 Turk's cap, or Pope's head. 



6. Mamillaria. 

 Plants globose, oblong or cylindrical^ seldom exceeding a foot 



