AND CONSERVATORY. 2G3 



CHAPTER XXIY. 



GREENEOUSE VERMIS. 



The insects which infest the plants usually grown in the 

 greenhouse are few in number, but capable of doing an 

 immense amount of mischief if not kept under with a strong 

 hand. 



Those which occasion the most trouble are green-fij, black 

 fly, thrips, red-spider, and scale. They are all more or less 

 destructive, and when once they obtain a firm footing in the 

 house are very difficult to eradicate. The first three are, 

 perhaps, the most easily disposed of, as they can be effectually 

 destroyed with tobacco-smoke, or by immersing the plants in 

 tobacco-water. The other two are the most persistent, and a 

 considerable amount of labour and perseverance will be found 

 necessary, as they cannot be dispersed with tobacco-smoke. 

 First of all, it is necessary to consider what the most favour- 

 able conditions are for the development of these pests, and 

 these may be said to consist in a dry and confined atmosphere, 

 and an unhealthy state of the plants, especially when brought 

 about by neglect in watering. In fact, it is the easiest 

 matter possible to produce a swarm of green-fly, or to have 

 the foliage of the plants smothered with red-spider, for it is 

 simply necessary to neglect the air-giving and watering for a 

 few days to ensure either of these results. Allow the venti- 

 lators to remain closed for two or three hours every day after 

 they should be opened, and insufficiently supply the plants 

 with water, and the cultivator will soon be supplied with suf- 

 ficient work to employ his head and his hands, and, moreover, 

 tax his patience, for, probably, the remaining part of the 

 season. The opposite of these conditions will, it may be 

 readily imagined, promote a vigorous growth, and check the 

 development of these pests. With a careful system of 

 watering and proper attention to air-givmg, there will not be 

 much trouble with either green-fly or red spider. The keeping 



