i9i i.] Tobacco Growing for Insecticidal Purposes. 383 



during the last week or two of growth. The ripening of the 

 leaves can be told by a distinct change in colour from a dark 

 to a lighter shade of green, but the exact time at which it is 

 best to cut is still undecided. The nicotine content of some 

 plants tested last summer increased by 1*5 per cent, during 

 the last ten days they were on the ground, so that it would 

 be better to cut the leaves when they are over ripe rather 

 than harvest them too early. 



There are two common methods of harvesting tobacco — 

 the Single Leaf method and the Whole Plant method. The 

 former method consists in picking the leaves off singly as 

 they become ripe and threading them on strings to dry. 

 The Whole Plant method consists in cutting the whole plant 

 when the middle leaves are ready, and hanging it up bodily 

 by the stem to dry without removing the leaves at all. The 

 second method is considerably the cheaper one, and so was 

 the one adopted at Wye last summer, the whole plant being 

 cut down level with the ground. The best instrument for the 

 purpose is a long-handled pair of pruning shears, but an 

 ordinary wood chopper will do the work quite well. 



Drying. — The plants should not be cut while dew is on the 

 leaves, as they are then very brittle and a number will fall 

 off. It is a good plan to leave them on the ground to wilt 

 for a few hours after cutting, the leaves gradually becoming 

 limp and then clinging better to the stem. The base of each 

 stem is then attached by means of a piece of string to a pole, 

 and a row of plants hung up to dry, either naturally in a 

 barn or with the help of a stove. Self-binder string recovered 

 from the threshing machine after being used the preceding 

 summer for binding sheaves of corn, was found to be just the 

 right length and texture for tying the plants to the poles. 



Stripping. — As soon as the leaves are drv they may be 

 stripped off the stems and stored away in a heap till the 

 time comes when they are required for spraying. As stated 

 above the best method of extraction is still being inves- 

 tigated, but soaking the cut-up leaves in water is 

 quite effective in extracting the greater portion of the 

 nicotine. It is certainly a simple way, and may be found to 

 be the cheapest method, even though by the aid of chemicals 

 a larger proportion of the nicotine may be extracted. 



