20, 6 Mendiola: Weight and Ash Content of Tobacco 641 
ash in the shaded plants than in those of the open. In the 
remaining cases the difference was in favor of the unshaded 
plants, but the difference was very slight. It is hardly neces- 
sary to point out that these results are not of much value to the 
present study, as only a part of the plant, the grain, was con- 
sidered. Thatcher gives us also an account of an experiment 
carried out by Murinoff, at the University of Halle, in which 
“etiolated” plants were compared with normal green plants. 
It was found that the percentage of ash was slightly higher in 
the normal green plants. 
Hasselbring, (10) in 1914, grew tobacco plants under cheese- 
cloth and in the open. Using entire plants in the analysis, he 
found that the absolute amounts of dry substance were about 
equal in the two sets, even if the plants in the open absorbed 
about 28 per cent more water than did the shaded ones. He 
found smaller amounts of ash in .the unshaded plants, but the 
difference is within the limits of individual variation in the same 
set. In another experiment the transpiration per unit area of 
leaf surface was nearly twice as great in the sun plants as in 
the shaded plants, but the total quantity of dry substance pro- 
duced was the same in both sets of plants. He considers these 
results as a suggestion that transpiration in itself, or the mere 
passage of water through the plant, has no influence on the 
assimilatory activity, provided the water supply does not fall 
below a certain minimum required to maintain the turgor of the 
cells. In conclusion he states that the absorption of salts by 
roots is independent of the absorption of water and that the 
transpiration stream does not exert an accelerating effect on the 
entrance of salts. : 
Kiesselbach, (11) in his study of transpiration as a factor in 
crop production, determined the effect of various factors upon 
the relation of transpiration to ash content. He grew corn 
plants in dry and humid greenhouses. Ash determinations were 
made of the entire plant. It was found that there was no ab- 
solute correlation between the percentage of ash and the quantity 
of water transpired per gram of ash content or the transpira- 
tion per m of dry matter. bs 
Fmiaene his Pee TE (12) in a recept paper on the relation- 
ship between the osmotic concentration of leaf sap and height of 
leaf insertion in trees, report that the relative concentration of 
electrolytes decreases from lower to higher levels, and this they 
take to indicate that the differences are due to increased pho- 
tosynthesis in the upper regions of the tree rather than to the 
