1904] BERGEN-—-TRANSPIRATION OF EVERGREENS 2g1 
the transpiration of the sun leaf and the shade leaf would be measured 
for unequal and rapidly diminishing amounts of contained water. 
Weighing whole plants growing in sealed pots is out of the question 
for large shrubs or trees, since seedlings which were small enough ° 
to be handled would fail to shade their own leaves and would not 
a 6b C d 
Fic. 6.—Transverse sections of leaves: A, sun leaf, and B, shade leaf of Olea; C, 
sun leaf, D, shade leaf of Quercus Ilex. Natural size. 
furnish leaves of typical adult form, size, and structure. Weighing 
leafy twigs with the cut ends immersed in water is not likely to afford 
the same absolute amounts of loss by transpiration as would be given 
by the same twigs supplied with water by the normal root pressure 
Fic. 7.—Sun leaves of Olea: the branch 
makes an angle of about 60° with the verti- 
cal, most of the leaves pointing somewhat 
vertically upward; in many other instances 
one leaf of each pair was found to point 
upward and the other downward. 
ee But the leaves are in a normal atmosphere, and their 
Same as *Sses (as compared with each other) may be very nearly the 
under absolutely natural conditions. 
the Mab: adopted in the experiments here recorded was to immerse 
¥ cut ends of the leafy twigs studied in water contained in 
y. 
