1914) 
DUGGAR AND COOLEY—FILMS AND TRANSPIRATION 19 
Ап examination of the data in the several tables involved 
in the pot experiments serve to indicate that while there is а 
certain amount of individual variation in the transpiration 
quantities of the various plants in any group, general conclu- 
sions seem to be warranted. Тһе individual variations in 
transpiration in the Bordeaux series are in closer accord with 
the variations in green weight of the plants used than are those 
in the other series. Taking all factors into consideration, а 
film of Bordeaux mixture is found to facilitate transpiration. 
Other films and dusts employed do not seem to affect the rate 
of transpiration to the same extent. 
In a consideration of the results in detail it is to be noted 
that the Bordeaux series (table іп) is not strictly comparable 
with the other (tables rv, v), since they were not conducted 
simultaneously. If the transpiration in grams per gram of 
green weight for the control (Bordeaux series) is represented 
by 100, then the rate for weak Bordeaux on this basis is 113.2, 
and the rate for strong Bordeaux is 125.43. Тһе differences 
are in the same direction, but not so great as those obtained 
with the potometer experiments. Тһе use of both weak and 
strong Bordeaux mixture materially strengthens the conclu- 
sions to be deduced. 
Тһе series which gives the results with other sprays and 
dusts is not so easily interpreted. Тһе transpiration quantities 
vary slightly on either side of the control, and no covering 
gives a negative difference (contrasted with the control) greater 
than six per cent (this is the case of Al(OH)s), or a positive 
difference greater than about eight per cent (charcoal). 
These slight average differences may be no more than would 
be explained by the possible experimental error; but it is of 
interest to perceive that, with the exception of clay, those 
surface applications which give lower values than the control 
are those which might diminish the absorption of heat in direct 
sunshine. Тһе results might then be the resultant of two 
factors, (1) the direct effect of the surface film or dust on the 
rate of water loss, and (2) the indirect effect exerted through 
a modification of the temperature of the leaf. 
Accepting as а general conclusion an acceleration of trans- 
piration (specifically in the castor bean and in the tomato) 
