73 
Porometer in Stomatal Investigation. 
Expt. 54. 11. xii. ’14 and 12. xii. ’14. 1 
Four chambers, A, B, c, D, were attached to one leaf of Ficus elastica at 
1 1.0 a.m., 1 1. xii. ’14, A, c and D being on one side of the midrib at a distance 
from the apex of about one-quarter, one-half, and three-quarters, respectively 
of the length of the leaf. B was on the other side of the midrib, about one- 
third of the leaf-length from the apex. 
Readings were taken at intervals from 12.40 p.m. till 4.30 p.m., 
December 11, and from 10.15 a.m. till 4.0 p.m. on December 12. The 
curves in Fig. 6 are the results of the latter series, the first series, which 
is not given, showing the closure due to shock and the subsequent recovery, 
which has already been discussed and illustrated. In the curves here 
shown there is not absolute coincidence, probably partly due to the different 
areas included under the respective chambers, but there is a very striking 
parallelism in all four curves, a change of direction in one being accompanied 
by similar changes in the others. The frequent irregularities were probably 
due to the varying illumination. 
The areas and mean readings were : 
A. 
Area i*o sq. cm. 
Mean reading . . . 0*142 
Reading per unit area 0*14 
B. 
i*2 sq. cm. 
0*171 
0*14 
C. 
o*8 sq. cm. 
0*117 
0*15 
D. 
j*i sq. cm. 
0*167 
o*!5 
These show good agreement, and indicate that if the numerical distribu- 
tion of stomata over the leaf-surface is regular, the stomatal pores in different 
regions of the leaf are open to the same extent under similar conditions. 
The distribution of stomata will be discussed later. 
Experiments upon Eucharis Mastersi and Eupatorium Raffilli gave 
similar results, and although exceptional readings are often found, it may be 
assumed that as a general rule in these plants the readings obtained with 
a porometer from one chamber on a leaf are indicative of the condition 
of stomata over the whole leaf. 
2. The type of experiment just described was repeated, with chambers 
on different leaves instead of on one leaf, with comparable though not 
exactly similar results. 
Expt. 70. 1. ii. ’15. 
Three similar chambers were fixed to different leaves of Eucharis 
Mastersi at 1.0 p.m. on 31. i. T5. 
A, to an old leaf, brown at the edges. 
B, to a mature healthy leaf. 
c, to a young leaf. 
Fig. 7 shows the curves obtained. These do not show the same 
parallelism as those in Expt. 54 previously described, but there is the same 
