64 
Knight . — On the Use of the 
leaf immediately adjacent to one of the chambers, so as to block the 
stomata over an area in the form of a ring around the chamber. This 
treatment increases the length of intercellular spaces to be traversed by the 
air-stream, and the difference between readings taken before and after 
vaselining will be due to the added resistance of the extra intercellular 
spaces, provided that the control chamber gives readings similar to those 
taken previously. By vaselining a portion of the leaf-surface a number 
of stomata are blocked, but as long as the unvaselined area is considerably 
greater than the area under the chamber the rate of the air-stream will not 
be limited by the unvaselined portion. 
Expt. 8. 2. xi. ’13. 
Two chambers, A and B, fixed one on each side of the midrib of leaf of 
Eucharis Mas ter si. 
Area of leaf under chambers : A, 1-4 sq. cm. ; B, 1-3 sq. cm. 
Area of leaf unvaselined outside the chambers : 
on A side of midrib, 106 sq. cm. 
y> B v » j) 1^3 >> 
Width of ring of vaseline, approx. o-8 cm. 
Thus the increase of length of intercellular spaces to be traversed was 
o-8 cm., and the unvaselined area was 75 to 95 times the area under the 
chamber. 
Table I. 
The readings are given in seconds and represent the time required to 
draw a given volume of air through the leaf. The vaseline was applied 
at 12.30 p.m. B was the control. 
A. B. 
Time . 
Reading . 
Time . 
Reading . 
12.15 p.m. 
12*8 
12.17 p.m. 
n *7 
12.25 
12'9 
12.27 
n *7 
12.30 p.m. 
[Vaselined] 
— 
— 
12.37 
23-1 
12.40 
13* 1 
12.47 
20*1 
12.50 
n*6 
12.57 
17*1 
1.0 
10*7 
1.25 
15*7 
1.27 
9-8 
2.8 
i6-i 
2.10 
io*5 
The immediate effect of vaselining was to reduce the rate of air-flow in 
both cases, which was to be expected in view of the fact already established 
that handling causes stomatal closure in Eucharis Mastersi . The decrease 
in rate was however much greater for A than for B, and by 2.10 p.m., when 
both had apparently recovered and the stomata were closing, presumably in 
response to some natural stimulus, the air-stream in A was still much slower 
than in B. By comparing in the case of A the two lowest readings (12-8 
and 15*7) we find that the rate has decreased by about 20 per cent, as a result 
of increasing the length of intercellular space traversed by only o-8 cm., at 
