156 Extension and Use of the Cacti. 



In general, it should be observed, that the species of Melocactus and Rhfpsalis, 

 as peculiarly belonging to the tropics, require the greatest degree of heat, and 

 are kept in houses at a moderate heat of at least + 15° Reaumur; to which may 

 be added the greater numher of the Cereus, some Epiphyllums, and Opuntias 

 of the valleys, and the greater number of the Pereskias. The Mammillarias and 

 Echinocacti of the higher plains of Mexico do not require so high a tempera- 

 ture; but they must have an equal heat all the year round, as the variations 

 of temperature are but little felt in their native localities. It is, on the con- 

 trary, very different with the Alpine and subalpine plants, such, for instance, 

 as Mammillaria vetula and M. supertexta, which, at a height of 11,000 ft. 

 stand the winter's cold, and must endure the frozen soil for the space of one 

 month ; and a still greater severity attends the wonderful Pereskias, Opuntias, 

 Cereuses, and Echinocacti of Chile and Peru, which grow to within a few 

 hundred feet of perpetual snow, and stand all the severity of an alpine winter, 

 with the tops of their stems sometimes covered with snow ; and how unsus- 

 ceptible of the variation in the temperature must those Opuntias and Mammillarias 

 be, which are situated on the northern and southern limits of their extension in 

 North America, under 4<9° north latitude, or on the Rocky Mountains, at 44?° 

 north latitude ; where their habitat is several thousand feet above the level of 

 the sea ! Here, also, may be mentioned the Opuntia italica, on account of its 

 wide extension in Europe, which is found under 47° north latitude, in the 

 warm alpine valleys ; and stands a cold, in winter, of from 6° to 8° of 

 Rdaumur. 



From what has been said, it may be seen that the climate which suits the 

 different kinds of Cacti extends from the heat of the tropics to the temperature 

 of the colder temperate regions ; and that, therefore, it is impossible to culti- 

 vate all the species with the same success, in the same degree of heat. It is 

 true, indeed, that many of the species can accommodate themselves, in some 

 degree, to a change of climate ; but the consequence would be an evident 

 alteration in their growth, and in the whole habit of the plant ; and even with 

 the most careful cultivation, particular species would vary from their normal 

 state, either in consequence of too much heat, or vice versa ; so that by such 

 treatment some would degenerate into wild plants, and produce formidable 

 thorns, or would be covered with wool, as they are in their native localities. 



It will also be unsuitable for the Melocacti, Cerei, and Opuntia;, which require 

 a hot-house, and are accustomed to a poor soil, to have an equal mixture of 

 soil to grow in ; for the Epiphylla which are parasitical, and obtain their 

 nourishment more or less from wood ; and for Mammillaria and Echinocacti of 

 the temperate zone, which grow on the most fruitful soil. 



In general, however, a nourishing and not too light a soil will be found 

 advantageous to all Cacti, if the moisture be supplied at the proper time, and 

 the period of their drought in their native country be observed, when they 

 should have very little or no water with us ; and plenty of water given, on the 

 contrary, when the rainy season of their native country comes on : and, as all 

 this refers to particular species, we can onby get the proper information of 

 their growth through the more attentive observations of travellers, which, 

 unfortunately, we have hitherto not been able to obtain. I have, therefore, 

 considered it of importance to add, in a note, some information on the native 

 soils of the Mexican Cacti, for which I am indebted to the kindness of Baron 

 von Karwinski.* 



* Where no particular kind of soil is mentioned, it may be understood to be 

 more or less of loam and rich soil. Cereus baxanus Karw., Cuba, on the sea shore, 

 on sand. Cereus ramosus Kariv., Epiphyllum latifrons Zucc, in the tropics, be- 

 tween Cordova and Vera Cruz, on clayey soil. — In the temperate parts (tierra 

 templada), near Zimapan, are found Cereus Dfckii Mart., C. erectus Karw., C. 

 geometrizans Mart., and C. dichroacanthus Mart., Echinocactus leucantha 

 Zucc., Mammillaria crucigera Mart., M. inuncta Hoffmsgg., Echinocactus ingens 

 Karw., Mammillaria columnaris, M. polythele, M. quadrispina Mart., on unpro- 



