lo4 BOTANICAL GAZETTE [ FEBRUARY 
changed, D meaning that the black 
velvet was drawn over the glass, L 
that it was removed. 
The first two changes at 11:27 
and 11:59 A.M. take place somewhat 
| slowly, ¢. ¢., from 6 to 10 minutes 
~ after the change in illumination, but 
7+38),4L = 
eeaean the later variations in the curve 
coincide very closely with the letters 
and B. The R-cool change at 
3:24 is smaller than the others. 
This is probably an instance of what 
is usually quite obvious, that late in 
the afternoon the stomata do not 
open when illuminated. 
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LA EXPERIMENT 77, fig. 75. May 23,1900. 
CAMPANULA PYRAMIDALIS. 
Campanula on bulb B, withered leaf on 
R; a B-cool fall in the curve means open- 
rj ing stomata. 
As in fig. rg, the letters D and L 
give the times at which the black 
ee velvet was replaced or withdrawn. 
The reaction time varies somewhat 
through the day, but in many cases 
the change in the curve follows very 
closely the change in illumination. 
BL 924g, 4, é., 40 minutes before 
sunset, the removal of the black 
cloth produced no effect. In my 
Observations on stomata, p. 596, I 
called attention to this fact, so that 
in this respect jig. 15 and other simi- 
lar results confirm my former work. 
But this refusal of the stomata to 
oe St at a time approximating to 
Fic. 15. cir natural hour for closing is the 
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