286 BOTANICAL GAZETTE [APRIL 
Conclusions 
Under the climatic conditions of Western Cuba the transpira- 
tion of tobacco plants grown in the open ground is nearly 30 per cent 
greater than the transpiration of plants grown under the cheese- 
cloth shade commonly used for shading tobacco in that region 
(fig. 1). The transpiration per unit area of leaf surface is nearly 
twice as great in the sun plants as in the shade plants. 
The shading of tobacco plants by this grade of cheese-cloth does 
not seem to result in a diminished production of total plant sub- 
stance by the shaded plants as compared with other like plants not 
shaded. Since, however, the leaves of the shade-grown plants have 
a much greater total area than those of plants grown in the open, 
it is evident that the quantity of plant material elaborated per unit 
of leaf area is greater in the plants grown in the open. 
Although the total production of dry plant substance is not 
influenced in any marked degree by the cheese-cloth shade, the dis- 
tribution of this substance is affected in such a manner that in the 
shade-grown plants relatively less material is deposited in the leaves 
and more in the stems than in the corresponding organs of the 
plants grown in full light. No evident influence is exerted on the 
deposition of material in the roots. 
BurEAv oF PLant INDUSTRY 
WasHincton, D.C. 
