TOBACCO INVESTIGATIONS. 35 



used, and in manj' instances with entirely negative results so far as killing 

 disease-producing organisms was concerned. 



It has been stated by some growers that they were absolutely sterilizing 

 their beds with low-pressure steam in the same time as with the high- 

 pressure outfits. There is no question but that certain types of soils will 

 permit the use of low-pressure, providing the soil is in exactly the right 

 mechanical condition and has a minimum water content. This has been 

 done experimentally and practically on light porous soils, but unless the 

 grower is assured by thermometer readings, or the complete cooking of 

 potatoes at the desired depth, that the soil is sterile, it is apt to be a 

 costly and futile undertaking. 



It is much safer to use high-pressure outfits, particularly when the 

 work is done by outside parties. In any event, the grower should assure 

 himself that he is sterilizing the soil and not merely killing a few weed 

 seeds. For general application the high-pressure method should be used; 

 the low-pressure method will sterilize, but economically it has only a very 

 limited range of apphcation on certain soils. Usually there is too much 

 guesswork in sterilization. 



Vitality of Tobacco Seed. 



It has been generally believed that the seed of tobacco retains its vitality 

 for a number of years, even up to twenty. This may be true in excep- 

 tional cases in which the seed has been preserved under ideal conditions, 

 but usually after the tenth year the vitality of our seed is so much reduced 

 as to render it unfit for use, even when preserved under the best conditions. 



A grower, however, often wishes to use a particular lot of seed a number 

 of years, and it is of interest to know approximately, at least, what the 

 germination of seed of the different varieties is at different ages. The 

 maintenance of vitality, of course, depends to a great extent on the con- 

 ditions under which the seed is kept, and this factor should be taken into 

 consideration in drawing conclusions as to the germinability of the seed. 

 In the following table are given some of the results obtained with seed of 

 different ages kept under excellent conditions in a cool, dry place, either 

 in nmslin bags or wide-mouthed glass containers plugged with cotton : — 



