1912] LIVINGSTON & BROWN—TRANSPIRATION 325 
Euphorbia gave variations equaling Physalis (tables II and III); 
those of Tribulus and Maclura were markedly less; while, as 
already noted, Prosopis and Covillea evidence very small variations, 
that of the latter rather definitely in the opposite direction. 
Scrutiny of table V brings out the fact that the hours of mini- 
mum relative water content for the prevailing type of leaves falls 
generally within an hour or two of that of the maximum evapora- 
TABLE V 
SUMMARY OF TABLES I-IV 
MINIMUM MOISTURE MAXIMUM MOISTURE MaximuM OF 
CONTENT CONTENT EVAPORATION 
PLANT 
Percentage Hour Percentage Hour cc. Hour 
Martynia (table I).. 77 14 85 20 4.02 16-17 
Sida (table I)...... 75 16 83 7 4.02 16-17 
Amarantus (table I) 79 16, 18 86 20, 24 4.02 16-17 
Clee acs De ey 13, 16 go 19, 21 2.94 14-15 
ysa 
(table HI). ..... 85 13 89 17,19,21| 5.08 12-13 
Physalis (3) 
(table IV)....... 87 15,173 88 13 2.52 13-14 
Nicotiana (table IT) 80 ey 85 5 2.04 14-15 
Euphorbia (table TI) 81 13 85 7 2.04 14-15 
(tabie TH) 205 - 89 13,17 92 7,9 2.04 14-15 
Tribulus (table II).. 78 9 81 587,23 2.94 14-15 
Maclura (table ITI) 63 15 70 7 5.08 12-13 
Covillea (table IIT). 54 7 58 16 5.08 12-13 
Prosopis (table III).| 59 9, 13 61 7, 16 5.08 | 12-13 
tion rate. The minimum moisture content occurs between 1:00 
P.M. and 5:00 P.M. for all cases except those already noted as 
exceptional, and that of Tribulus (table II), which has its minimum 
at 9:00 A.M. 
The evidence from Physalis, indicating clearly a definite relation 
between the magnitude of the moisture variation and the intensity 
of evaporation, may be interpreted to mean that the variation is 
due primarily to incipient drying (to a removal of water by tran- 
spiration more rapidly than its entrance into the leaves), and not 
to an accumulation of non-aqueous bodies in the leaf cells. It 
seems extremely improbable that a diurnal accumulation of plastic 
materials should exhibit such a parallelism with the evaporation 
