426 BOTANICAL GAZETTE [JUNE 
The outline of the leaves used was carefully traced on paper and 
the area measured with a planimeter. The results thus obtained 
were computed and expressed as grams of water transpired per 
hour per sq. cm. A sample record sheet is herewith given, showing 
the records as made in the field. 
TRANSPIRATION TEST NO. 2 TRANSPIRATION TEST NO. 3 
July 13, 1912 July 13, 1912 
Healthy York Imperial leaves Diseased York Imperial leaves 
Temperature... . : 20.5 C. aemperature.... age C 
No. of leaves in test. I No. of leaves in test. . I 
Area of leaves. :...... 21.3 sq.cm. ‘Area of leaves....... 35.2 sq. cm. 
Vol. of air used...... 19 liters Vol, of air ised . 3: 19 liters 
Exper’t began 10:18 A.M. Exper’t began....... 10:14 A.M 
Expert ended... .... 11:20 A.M. . t — ep eds 11:16 A.M 
eee 62 min. Seeeen. et ...f. 62 min. 
Final wt. of tube. .... O1.555 gm. etal wt. as tube... . 99.675 gm. 
Initial wt. of tube....91.185 gm. Initial wt. of tube... .99. 297 gm. 
Dierenee os ieee ck: 0.370 gm. AMTONE a 0.378 gm. 
Water in equiv. vol. Water in equiv. vol. 
Wie ah is oy es ©. 291 gm. oe ere ere . 291 gm 
Water from leaves.... 0.079 gm. Water from leaves.... 0.087 gm. 
heeds per hr. per sq. Water per hr. per sq. 
Peg a ee es 0.0036 gm, irc tie eas oO ees On. 
There were 52 determinations made upon healthy and diseased 
leaves of the York Imperial and 26 upon leaves of the Ben Davis. 
The results are presented in tabular form in tables I and II. 
An inspection of the tables shows that the unit transpiration 
of the diseased leaves of both varieties of apples was in the majority 
of cases less than that of the healthy, although exceptions are to 
be noted. Some of these discrepancies may have arisen from 
unguarded errors of ——— but it is not probable that all 
are due to such cause. 
It is not apparent that the ratio between the transpiration in 
the healthy and diseased leaves was subject to any regular hourly 
variation. The unit transpiration in each case naturally varied 
from hour to hour, but the ratios were in general the same at any 
given period of the day. 
The average ratio of transpiration in the diseased and healthy 
