Grown in fnll direct Knnlii^ht 

 Grown in bhade 



66 



Tbe elal3orat)Oii of nicotine, according to these figures, increased reg- 

 ularly with tbe increase in temperature. 



Tbe effect of ligbt was observed by comparing tbe development of 

 nicotine in plants grown in tbe sunligbt with that of tbose sbaded on 

 all sides except tbe nortb side, tbus receiving no direct liglit, or tbose 

 grown in tbe sunbgbt but baviug a number of leaves covered with tin 

 foil. Plants grown under tbese different conditions contained tbe fol- 

 lowing percentages of nicotine : 



Per cent. 



M-y 



s i.r» 

 ri'^ 



Leaves fully exposed to light . J^r^" .^; ' ^^ g 



, X 1 T J S No. 1..2.-2 



Leaves of same plants shaded ) ^a 2 35 



Altliongb tbe variations in nicotine content werc'(|nite largo in plants 

 receiving like treatment, tbe dill'erences in tbis respect between i»bints 

 receiving unlike treatment were greater, and indicate tbat direct sun- 

 ligbt bad a favorable influence on tbe formation of nicotine, and furtber, 

 tbat tbis ell'ect is to a considerable extent bx'al, since tbe leaves exi)osed 

 to tbe sunligbt produced twice as mucb nicotine as tbose on tbe same 

 plants wliicli were slmded. Tbe autbor bas sbown on previous occa- 

 sions tbat tobacco ricb in nicotine is in general dark col()re<l. He sug- 

 gests tbat since tbe production of nicotine is favored by ligbt, it may be 

 possible to produce relatively ligbt or dark leaves by cultivating tbe 

 plants close together or fartlier apart. 



To study tbe effects of water in tbe soil, an attemi^t was made tosuj)- 

 ply respectively 80, 00, and 40 per cent of tbe amount of water by 

 weight which the soil was capable of absorbing, an<l though rains i)ns 

 vented tbis ])b»n from being accurately carried out, Ihese conditions of 

 soil moisture were approximated. Tbe plants grown under tbe differ- 

 ent conditions contained the following percentages of nicotine : 



Pdcoiiagcs of nicotine. 



The plants receiving the largest quantity of water produced tbe least 

 dry matter, and tbose which were protected from the rain and kej^t 

 quite dry, tbe most dry matter. The production of organic matter and of 

 nicotine was thus hindered by tbe presence of large (juantities of water 

 in the soil. These results, in the opinion of the autbor, corroborate 



* Harvested one month earlier. 



