488 
Delf. — Transpiration and Behaviour of 
TABLE I 
Measurements op Diameter of a Single Internode at Different Levels . 
Level. 
(0 
.(«■) 
A 
3.25 mm. 
3*8 mm. 
B 
3*37 5 > 
3*7 „ 
C 
2-75 >, 
3 -i „ 
D 
2*35 » 
2*55 >, 
E 
2.1 „ 
2 ‘0I ,, 
Average diameter 2-898 mm. 
The levels at which the measurements were made are shown in 
Fig. 4 (i). At the level B the cross-section is roughly elliptical in outline ; 
at the level E the outline of a cross-section would be almost perfectly cir- 
cular. In this experiment measurements of the greatest and least diameter 
Fig. 4. (i) Internode of a shoot of Fig. 5. Showing at A the short glass rod from 
Salicornia annua , from which measure- which the celluloidin film B was obtained, 
ments recorded in Table I were made, at the 
levels A, B, c, D, E. In (ii) are shown 
the outlines of cross-section at the levels 
b and E. 
were made at each level (Table I, columns (i) and (ii)). The mean of all 
these readings is nearly 2-90 mm., and the mean of the two readings at the 
level c is 2*92 mm. Thus for all practical purposes the mean diameter just 
below the widest part of the internode represents the mean diameter for 
that internode. These readings can, with a little practice, be made easily 
and quickly on the growing shoot, and thus errors due to shrinkage during 
manipulation are avoided, but some care must be taken not to bruise the 
surface of the plant when adjusting the micrometer screw. 
At first sight this method may seem too rough to be of any value for 
quantitative work, but the following experiments show that the error is less 
than might have been anticipated. 
A length of 3 cm. was first marked off with Indian ink on a short 
glass rod. The distance between the marks was read with a lens magni- 
fying ten times, and the mean of three readings gave the mean length 
