: ld ones, 
1904] BERGEN—RELATIVE TRANSPIRATION OF LEAVES 449 
the former contains averages based on a larger number of determina- 
tions for each species. : 
TRANSPIRATION RATIOS; EQUAL WEIGHTS. 
o> 
Quercus Ilex - 0. eS eee 2.73 
Smilax aspera - Me a 
Viburnum Tinus - - - ee 
In two species, the Rhamnus and the Hedera, the old leaves are 
seen to be notably deficient in capacity for transpiration. In the 
former this fact is very possibly due to the moribund condition of the 
old leaves, which at the time of observation were about to turn yellow 
and fall. In the latter, the leaves were not ready to fall, and some 
other explanation of their sluggish action needs to be sought. 
In view of the marked differences in transpiration between the 
dld and the new leaves of most of the species studied, it seemed 
Worth while to investigate the question whether these differences 
Were accentuated or diminished by covering the stomatal surface 
(the lower one) with wax and so comparing the normal transpiration 
with the epidermal taken alone. This inquiry was not undertaken 
until so late in the season that only a portion of the comparisons 
Which it would have been desirable to make were possible. The 
Most convenient way of expressing the results seemed to be to give 
the ratio, Joss of water by plain leaf divided by loss of water by waxed 
leaj, first for the old leaves, then for the new ones, of each species 
examined. 
TRANSPIRATION RATIOS; PLAIN AND WAXED LEAVES 
PLAIN + WAXED 
Old leaves New leaves 
Olea europaea...........++. 2.62 3-77 
Nerium Oleander..........- 3-52. 12.75 
Pistacia Lentiscus........... 3-00 5°33 
dlédera Helix... .........<.% 2.93 6.80 
In the Species examined it is evident that the total transpiration 
Is the epidermal alone much more in the new leaves than the 
Examination of the actual amounts of moisture lost in 
1 “th case leads me to suppose that this inequality is due to the 
