GENERAL TREATMENT. 



183 



or twice a-week ; but during autumn and winter, this should be dis- 

 continued. 



Air cannot be too freely admitted to them at all seasons, both in winter 

 and summer ; and dming the latter period, the side lights of the Succulent 

 house, at least that portion of it dedicated to the families Sempervivumj 

 Crasmlu, Mesemhryanthemuyn, SiC, should be altogether removed : that 

 portion in which Sfapelia, CactecB, &c., are kept, should only be thus 

 openly exposed in very warm days, but a partial degree of ventilation 

 must be given them upon all fitting occasions. 



A watchful eye must be kept that the smaller and more delicate do not 

 suffer from damp, and that cuttings of those apparently likely to die 

 or become unsightly be put in, for many of the more curious are not 

 long-hved. Frequent cleaning the smface of the mould in the pots ; 

 examining them minutely for the detection of insects, which they are 

 liable to, particularly the scale, white bug, and green fly; rubbing off 

 the former with a sponge and soft soap, washing the second off with clear 

 water applied by the engine, and using tobacco smoke, or Scotch snuff 

 sprinkled over them, when damp from previous watering, will completely 

 rid them of these enemies. 



There are two curious and often fatal diseases to which some succulent 

 plants are subject, particularly the genus Opuntia, and some other of the 

 Cactece ; and these are admirably described by M. Thiery de Menonville, 

 who travelled, many years since, through the Spanish settlements of South 

 America. These diseases are termed by him the gangrene and la dissolu- 

 tion. The former of these is of frequent occurrence, beginning with a 

 black spot, which spreads till the whole plant ultimately dies. The latter 

 disease is very appropriately called la dissolution, and is much more serious 

 in its effects than the former : it is described by the late eminent Sir 

 James Edward Smith, in Introduction to Physiological and Systematic 

 Botany," as follows : — This seems to be a sudden decay of the vital 

 principle, Hke that produced in animals by Hghtning or strong electricity. 

 In an hour's time, from some unknown cause, a joint, a whole branch, or 

 sometimes an entire plant of the nopal (the Indian name for the Opuntia 

 cochinillifera or Indian fig), changes from a state of apparent health to a 

 state of putrefaction or dissolution. One minute its surface is verdant 

 and shining ; the next it tm'ns yellow, and all its brilliancy is gone. On 

 cutting into this substance, the inside is found to have lost all cohesion, 

 being quite rotten. The only remedy in this case is speedy amputation 

 below the diseased part." Both these diseases are not unfrequently ob- 

 served in collections in this country, and if the former be not arrested in 



