320 THE GREENHOUSE. [CHAP. XI. 



much air and light as possible. The water 

 should never be suffered to stand in the saucer 

 of any succulent plant; but it should be given 

 regularly, diminishing the quantity a little every 

 day as the season for rest approaches. If the 

 water be suddenly stopped, the leaves of the 

 plants will shrink and become flaccid, and, 

 when this is the case, the plant generally dies. 

 A deficiency of air, on the other hand, will 

 cause the plant to damp off. All mesembry- 

 anthenmms are very soon affected by frost, but 

 will thrive in the open air in summer. 



The Cactacece, which are also succulent plants, 

 are arranged in several quite distinct "roups, 

 which require different treatment. The first 

 of these comprises the various kinds of Tree 

 Cereus, which have long slender stems thirty 

 or forty feet high, without either branches or 

 leaves. These singular-looking plants grow on 

 the summit of the mountains of Brazil, in a 

 poor, dry, stony soil, and exposed on every 

 side to the cold breezes of the lofty regions they 

 inhabit. In England they should be kept in 

 only greenhouse heat, even in winter ; and they 

 should have abundance of light and air ; while 

 they should be grown in pots well drained 

 with cinders, and rilled up with a mixture of 

 loam and pounded brick and lime rubbish. The 

 Mammillarias and Echinocacti, forming the 

 group called the Porcupine Cacti, grow in the 

 valleys of the temperate regions, generally in 

 loamy soil, and among thick short grass, passing 

 half their year in continual rain. The Opuntia, 

 sometimes called the Prickly Pear, and some- 

 times the Indian Fig, is known by its flat oval 

 leaves or rather stems, and its prickly but 



