II. THE METHODS OF RAISING THE EXPERIMENTAL 



PLANTS. 



The methods employed at Pusa in raising the experimental 

 plants have already been fully described^ in a previous paper, 

 and it will only be necessary briefly to recapitulate them. In 

 experimental work on tobacco, the two most important points 

 are: (1) to raise the seedlings Avithout contamination, and (2) 

 to eliminate, as far as possible, all differences due to environ- 

 mental influences. 



The seeds of the tobacco are so small that they are very 

 easily carried from one culture to another by wind, rain, earth- 

 worms, or by the hands of the workmen. The seed is broAvn and 

 indistinguishable from the soil, and retains its vitality, even 

 under adverse conditions, for several years. The practice 

 adopted at Pusa is to raise the seedlings in large shallow boxes, 

 and every precaution is taken to collect the earth and leaf- 

 mould from places Avhere contamination by stray tobacco seed 

 is impossible. The boxes are made up about six weeks before 

 sowingandkept moist, so as to cause any stray seeds to germinate. 

 So far (1908 to 1912) no tobacco seedlings have been found in the 

 boxes prior to sowing. The boxes are sown, one at a time, 

 and the sower has to wash his hands before sowing another box. 

 After sowing each box it is immediately removed into the shade 

 till the seedlings appear. They are then enclosed in a wire 

 netting fence to keep off animals, and are placed so far apart 

 that the earth from one box cannot be splashed on to an adjacent 

 one by the sudden tropical storms which sometimes occur 

 at this season. Precautions are taken during the process of 

 thinning to prevent admixture and this operation is only 



* Howard and Howard, I.e. 



