192 GKEENHOUSB MANAGEMENT. 



same way and will tend to keep the fly in check. As 

 soon as the presence of green fly can be detected, the 

 house should be SUed with tobacco smoke. This should 

 be repeated at the end of two or three days, and, if 

 properly done, the aphides will be destroyed. 



As the insects develop, the tobacco smoke does not 

 seem powerful enough to destroy them, and if for any 

 reason fumigation has been neglected too long to be 

 effective, resort must be had to some other insecticide. 

 A strong decoction of tobacco stems and tobacco extract 

 'vill destroy them, while pyrethrum or buhach seems 

 quite effectual as a remedy against adult aphides, and 

 may be put on as a dry powder with a bellows, or in 

 water with a syringe, using at the rate of a tablespoon- 

 ful to a gallon. When the houses are large, a small 

 spraying pump will be convenient for applying these 

 and similar insecticides. 



When given proper conditions, the beds planted the 

 first of October can be cut for Thanksgiving purposes, 

 and can be cleaned out ready to be reset by the first of 

 December, The next crop will develop by the first of 

 February, and the third crop will be off by the first of 

 April. Under especially favorable conditions, two or 

 three weeks can be gained upon this, which will allow a 

 fourth crop to be taken off by the middle of April. 



About two months should be allowed for growing 

 the plants after sowing the seed, and seven or eight 

 weeks more for the growth of the heads after planting 

 out. This will be none too much during the cloudy and 

 short days of ISTovember and December, but as the sun 

 gets higher in February and March, six weeks will gen- 

 erally suffice. 



In marketing lettuce, the heads are placed verti- 

 cally in baskets or boxes (Fig. 73) when supplied to the 

 local trade, or in barrels for distant shipment. It is 

 best to pack the cabbage sorts with the stems up, while 



