1906] SPALDING—ABSORPTION OF WATER BY LEAVES 277 
ABLE X. 
PARKINSONIA TORREYANA. SEEDLINGS. December 1904. 
. Weight in|Loss or gain Boa 
No.| Date | Time | erin per cent. Conditions 
t | Dee. 31 | -g232 AM. | 0.901 
12:45 P.M. | 0.944 | 1.8 loss | After repeatedly immersing in water 
2 9.37 A.M. | 0.886 gtd drying, aera! be gees at- 
5 tempts to i the s 
12°52 P.M. | Ovd55 | 3.5408 
phylla and P. Torreyana, the conclusion must be drawn that the 
species of Parkinsonia represented here either absorb no water, or at 
most an exceedingly small quantity, through their leaves. Before 
making the experimental test it was thought that the fresh, rapidly 
transpiring leaves of seedlings might exhibit a capacity for absorption 
not shown by those of older plants, but this has not proven to be the case. 
Prosopis velutina. 
Work on the mesquite was carried on at intervals for a number 
of weeks in January, February, and March, the material first em- 
ployed being obtained from mature specimens, while in the later 
experiments seedlings were used. Of specimens taken from mature 
plants only the leaves were immersed in water. In some cases 
the upper surface resisted wetting, while in others both surfaces 
were easily wetted. This was followed, as indicated by some increase 
of weight, by absorption of water in limited quantities. The seed- 
lings which were employed in subsequent experiments remained 
unwetted in all cases when they were immersed in water, and in spite 
of the fact that two of the specimens had been left to dry as much as 
forty-two hours and showed the effects of this treatment before im- 
mersion, there is no evidence that they absorbed any water whatever. 
It is apparent, then, that as long as the leaves of the mesquite 
are perfect and resist wetting they absorb no water, even after dry- 
ing for some time, but that they may absorb more or less after they 
have become old and can be wetted. It is very questionable, to 
say the least, whether in the latter case this process has any physi- 
ological significance. It would seem that in the mesquite, as in 
the palo verde, adaptations to xerophytic conditions have been 
carried so far in the direction of preventing excessive transpiration 
that leaf absorption, as a normal process, does not take place. 
