362 Curtis: SOME OBSERVATIONS ON TRANSPIRATION 
is sealed to a test-tube and the loss in weight is viewed witha hori- 
zontal microscope or in Gardner’s experiment where the transpi- 
ration stream of a small shoot is viewed under a microscope. In 
both of these latter cases the transpiration rate can be examined in 
short intervals of time and we have a magnified view, so to speak, 
of the process. In all these methods the irregularity of the rate 
is the striking phenomenon. It is ever fluctuating and without 
apparent reason. It is exceptional to find consecutive readings 
that show a fixed ratio of increase or decrease. In the above 
table while the hourly weighings furnish singular irregularities 
they give an imperfect idea of the endless series of changes that 
are constantly going on. 
In the curve found for Adwtilon, the acceleration though con- 
tinuing for eight hours (a very exceptional curve) increases very 
irregularly, 7. ¢., by 83 mg. 73, 50, 38, 98, 41, 72, and then declines 
by 29, 50, rises again by 11 and finally declines by 5,337—the 
last evidently a light effect. In the case of K/einia and Acalypha 
an irregular decline follows for three hours when the rate for 
Kleinia accelerates for six hours and then declines, while in the 
case of Acalypha there is a rise for two hours followed by 4 de- 
cline for one hour, then a rise for three hours, then a decline for 
three hours, then a rise for one hour. The succeeding hour, not 
given in the table, showed a further decline, 2. ¢., 96 but still in eX- 
cess of the rate at 5 o'clock. I was able to verify the character 
of these fluctuations during the summer of 1go! at the N. Y. 
Botanical Garden and it gives me pleasure to acknowledge the 
facilities for conducting the work that were placed at my disposal. 
It would seem that these variations can only very indirectly 
be connected with external conditions and the facts would appe@” 
to warrant the conclusion that the phenomena here recorded are 
the expression of the vital processes at work in the plant. " 
should be said that in all the experiments recorded in this paper 
that care was taken to select thrifty potted plants and the a 
were placed in large tin cans, the mouths being closed with t” 
covers and sealed with beeswax mixture after the manner SUS” 
gested by Darwin. In this way a considerable volume of air was 
at the disposal of the roots and would serve to keep the plant ® 
normal condition for some time. It was necessary to make 
