t9g09] BERGEN—TRANSPIRATION IN YOUNG SEEDLINGS 281 
tions abnormal for the kinds of plants studied. If the atmosphere 
were to be made very dry, the leaves grown in very damp air would 
wilt inside of five minutes or less and die in a comparatively short 
time. In some cases it was found best to determine the transpiration 
of readily wilted leaves for a period of fifteen minutes and compare 
TRANSPIRATION RATIOS 
Kind of leaf Rel. humid. during trans. period | Ratio M/D 
Phaseolus 25 { 2.2 
Phaseolus 63 2.5 
Phaseolus.........- 64 3:2 
LAPINUSS. 32 ok 26 4.0 
DDI OUS . 25:5: o as , about 43 8.2 
GUDINUS, fess ee ae | about 38 To.0 
LUpinus.ccss5 eee | variable, probably over 40 1.9* 
Mirabilis. iH 36 3-9 
Mirabilis... 2. 603 29 4.8 
Tpomoea.)....4,. 080. 26 / 7-4 
SAW Sos seca 34 6.6 
OAiVide aA ee Fin 8.9 
SINE PIS ss gc ks 28 3-5 
Snewmis. ge 24 3g 
Cueumia:s. so is20s 34 | 9-3 
Mieptiaia... co.cc about 50 oe 
* Young leaves, only half grown or less. 
t The moist-air leaves transpired on May 42 in air of 28 per cent. relative humidity, and the dry-air 
ones on May 13 in air of 34 per cent, relative humidity. 
this with the (calculated) fifteen-minute loss of the dry-air leaf of the 
same species, allowed to transpire for one or two hours. Oxalis 
corniculata from saturated air became wholly wilted inside of one 
minute, on being removed from the glass case, so its transpiration 
tatio could not be determined. It would be interesting to compare the 
Telative transpiration of the two kinds of leaves in extremely dry 
air minute by minute, but weighings on a balance delicate enough 
for this purpose could not be made with sufficient rapidity. 
The conditions as regards relative humidity were intentionally 
Varied a good deal, in order to show whether the transpiration ratios 
follow closely the changes in humidity. It is evident that in Phaseolus 
and Lupinus they do not. 
hile no experiments were made with a view of measuring the 
absolute rates of transpiration of the plants studied, all under the 
same conditions of temperature and humidity, it may be worth 
