1921] CRIBBS—TILIA AMERICANA 205 
responding elevation on those of temperature, evaporation, and 
saturation deficit of the air. The height of the rise was on the 
whole rather unexpected, inasmuch as the late afternoon was 
regularly characterized by a steady decline, during which time the 
stomata were closing. Similar reactions during brief periods of 
Precipitation were recorded during investigation on the dunes, 
where the depressions were commonly less pronounced. 
5 
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4 ajo 
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1jeo 2joo 300 4jeo 3100 BOO on 
BWwOo TWO #109 gh00 40409 nico 12jo0 
Fic, 6.—Data for station J, taken September 3, showing depression in at 
tion as result of visible wilting caused by abscission; third solid line represents cuticular 
. transpiration as recorded for adaxial side of leaf; note low temperature in morning. 
ABSCISSION.—Fig. 6 shows a curve which is strikingly different 
from the typical one recorded during this work. It is characterized 
by a rapid rise to a fairly high maximum which occurred early, 
about 9:00 A.M. Following the maximum there was a decline, which 
by midday had almost reached the level of cuticular transpiration. 
This condition prevailed throughout the remainder of the day, there 
being a slight and very gradual rise until about 5:00 o'clock. The 
mesophyll saturation deficit recorded is very conspicuous. This 
curve is very similar to those described as occurring at stations A 
and B on the dunes taken on August 26 (fig. 9, graph 3). In that 
