688 
BOTANY: H. H. M. BOWMAN 
For the soils series of experiments the data show that the most strik- 
ing phenomenon is the accelerating effect on the transpiration due to 
the soil from Maplewood, New Jersey. It is assumed that this accelerat- 
ing effect is due to chemical action, the New Jersey soil having a larger 
number of elements in it, and others in greater amount (viz., iron, alu- 
minium, and silica) than in the shell sand of the Tortugas, in which 
calcium carbonate preponderates. Though, unfortunately, the range 
of data is not wide enough on the New Jersey soil to produce a full 
curve, there is enough to show that the segment paralleled the para- 
bola of the shell sand curve, which curve is expressed with the con- 
centration of the water being constant for both soils. 
Another interesting point, illustrated in this latter plotting, particu- 
larly of the data secured on the cultures which were kept merely moist 
with the salt water, was the demonstration of the physiological law 
that the smaller the quantity of available moisture the slower the 
transpiration. Of course, this was only to be expected, but the clarity 
of the evidence presented in this case was a pleasant surprise to the 
investigator, inasmuch as he was only indirectly concerned with the 
water available for absorption. 
Casual mention may here be made also of a series of biochemical 
tests conducted on Rhizophora hypocotyls this summer, to determine 
the relations of the amounts of tannic acid and dextrose in these organs; 
and also to demonstrate, if possible, the presence of the enzyme tannase 
— broadly, to learn something of the role of tannin, which is so abundant 
in Rhizophora in nearly all its tissues. This work, while merely started, 
presents a very interesting field of investigation, since it is supposed 
that some tannins of the plastic group probably contribute to the nu- 
trition of the plants containing them. It is hoped to continue work 
on this problem, since the knowledge of the function of tannins in the 
plant economy is rather obscure, and generally they are supposed to 
be merely excretory products. On account of the paucity of data in 
this research the writer does not feel justified in making a definite state- 
ment regarding the relation of the amounts of tannic acid and dextrose 
in the Rhizophora hypocotyl; at present, however, it may be safely said, 
on the strength of over 50 tests for tannase, conducted according to the 
usual methods of enzyme tests, that this enzyme could not be detected 
in the hypocotyl of Rhizophora. 
