258 BOTANICAL GAZETTE [APRIL 
hand?" Second, in view of the fact that a large portion of the 
tobacco crop is grown regularly under shade, such data would not 
be devoid of practical interest, especially in regions like Western 
Cuba, where annual crops require irrigation and where much of the 
irrigation is accomplished by toilsome hand labor. Finally, in the 
minds of investigators, transpiration has frequently been associated 
with assimilation. The water requirement of agricultural crops 
has usually been stated in a ratio of the quantity of water tran- 
spired to dry substance produced. As a rule, this ratio has been 
considered merely as a convenient empirical expression of the 
water-utilization of plants; but some writers have assumed a closer 
relation and have postulated a direct influence of transpiration on 
production, or conversely. Therefore, it is of interest to determine 
to what extent the conditions induced by shade, either directly or 
through their influence on transpiration, affect production. 
For these reasons, the work described in the following pages was 
undertaken at the Cuban Agricultural Experiment Station at 
Santiago de las Vegas during the season of 1908-1909. For con- 
stant and ready aid in carrying out the exacting work required for 
this investigation, I am much indebted to ENRIQUE IBANEZ and 
AvcuSTIN GaRCIA, at that time my assistants at the station. 
Environment 
GENERAL STATEMENT 
For the purpose of these experiments, six tobacco plants were 
grown in the open ground, and six under cheese-cloth shade in 4 
manner described later. The cheese-cloth was of the kind generally 
used in Cuba and elsewhere for shading tobacco (fig. 1). During 
the middle of the day, when the sun’s rays are nearly perpendicular, 
this cloth casts a barely perceptible shadow, which, however, 'S 
more noticeable early in the morning or late in the afternoon. In 
. FITTBOGEN indeed grew to maturity some plants of oats in a greenhous¢ and 
others in the open. He regarded the loss of light due to its passage through ee 
glass as one of the factors tending to lower the transpiration of the plants. This 
experiment, however, can hardly be classed as a study of the effect of shading 08 
transpiration. Fitrsocen, J., Uber Wasserverdunstung der Haferpflanze "0 2 
verschiedenen Warme-, Licht-, und Luftfeuchtigkeits-Verhiltnissen. Landw. J 
3:141-146. 1874.” 
