70 
WILLIAM H. BROWN 
tion. The percentages thus derived are presented, for nine different 
leaves, in Table II, which includes the data for the leaves referred to 
in Table I with the corresponding experiment numbers. 
Table I. 
Comparative Measurements of Distances Between Adjacefit Dots on the Lower Surface of 
Dionaea Leaves Before and After the Closing Movement, the Dots Arranged in 
a Line Transverse to the Midrib 
Experiment No. 
Leaf Open 
Leaf Closed 
Leaf Open 
Leaf Closed 
Leaf Open 
Leaf Close 
\ a 
20. 0 
22.0 
20.0 
23.0 
23.0 
23.0 
b 
23.0 
23-5 
23-5 
26.0 
27.0 
28.0 
I 
c 
23.0 
29.0 
30.0 
34-0 
34-0 
35-0 
d 
30:0 
34-0 
35-0 
36.0 
36.0 
38.0 
e 
19.0 
19.0 
20.0 
. 21.0 
21.5 
\ a 
21.0 
22.0 
b 
26.0 
28.0 
.... 
2 < 
c 
37-0 
40.5 
d 
25.0 
26.5 
e 
26.0 
27.0 
I a 
23.0 
23.0 
24.0 
b 
31.0 
32.0 
33.0 
.... 
3 < 
c 
26.0 
29.0 
29.0 
d 
21.0 
22,0 
23.0 
la 
25.0 
27.0 
b 
17.0 
18.0 
4< 
c 
17.0 
19.0 
d 
16.0 
17-5 
From the data of Table II it appears that the lower surface of the 
leaf lobe expands transversely during the process of closing, the 
average amount of this expansion for the leaves tested being 6.7 
percent of the original distance from the first to the last dot. 
The results of similar measurements of the distances between 
dots placed in rows parallel to the midrib gave similar results, and it 
thus appears that the area of the whole lower surface increases 
in extent during closure. 
Open leaves are usually slightly curved so that the dorsal surface 
is somewhat concave and the ventral convex. During the process of 
closing, with this type of movement, as has been remarked, this curva- 
ture becomes much more pronounced. Since the measurements did 
not give the distances between the dots along the curved surface, but 
only the rectilinear distances, the amounts of expansion shown in Table 
I are less than those actually occurring. The distance measured was 
always the chord of the arc of curvature of the leaf surface. 
