CULTURE OF THE TRIBES OF CACTUSES. 55 



They thrive well in summer kept in the open air, without any cover- 

 ing, if they are allowed to have plenty of water. With this treat- 

 ment there is little danger of the plants being attacked by red spider 

 or scale. But should Spider appear, I know of no better means of 

 getting rid of it than by sprinkling the plants thickly with flowers of 

 sulphur ; and an abundant washing with clean water with a syringe 

 helps to destroy the scale. The treatment of cactuses during 

 winter is very different from that in summer. In their native 

 country the dry time of year has the same effect upon those plants 

 as winter has' on ours, namely, it produces a state of rest. In this 

 state, if they are to remain in health, and flower the following sum- 

 mer, they should not be removed to a cold greenhouse, for in their 

 native country they do not arrive at maturity through cold, but by 

 the dryness of their situation. Indeed, the experience of many years 

 has taught me that they thrive well if they are kept in a hot-house. 



When they are removed in autumn from the open air into a hot- 

 house, do not leave off watering them immediately, because that 

 would interrupt vegetation too suddenly ; but continue to water them 

 regularly until nearly the end of the year, only not so abundantly as 

 before, and stop it by degrees until the end of December, when it 

 must be discontinued altogether. From this time to the period when 

 the plants can be again placed in the open air they need no water, 

 not even if they should begin to dry up or to shrivel, for there is no 

 danger of their being injured by getting into that state ; but great 

 disadvantage would arise from watering them, and many specimens 

 might be lost. No doubt when watering is discontinued roots are apt 

 to die off, because being less succulent than the plant itself they soon 

 lose their moisture which cannot be replaced out of the dry earth. 

 This, however, does not harm the plants in a dry state, but at a later 

 period, when watering is renewed, it then may have disadvantageous 

 consequences, for it is then found that the dead and withered roots easily 

 decay, and this communicates itself by degrees to the centre of the plant, 

 which then speedily perishes. It is, therefore, indispensable that 

 the plants should be examined in order to see whether rottenness is 

 beginning ; for if this is discovered too late, there is no remed)', and 

 the decay will extend, and destroy the plants. 



There is no great difficulty in the propagation of them. However, 

 there are many, especially among the better and rarer sorts, that are 



