Stomata in Halophytes . 489 
between the marks. The diameter was measured with a micrometer screw. 
The rod was now dipped into a solution made by dissolving Schering’s 
celluloidin in equal parts of alcohol and ether. On withdrawing the rod 
and turning it gently for one to two minutes, a firm film was formed over 
the whole of the glass rod. This was now cut as nearly as possible above 
the Indian ink marks, and split along its length with a sharp knife, so that 
a small and nearly rectangular film was removed from the measured region 
of the glass rod. The film was immediately placed with the inner side 
downwards upon paper ruled in millimetre squares, and the area found. 
After a few trial experiments it was possible to make a film which gave the 
area correct to within 2 %. 
Fig. 5 shows at A a short glass rod marked with Indian ink at two 
places, 3 cm. apart ; and at B the outline of the film which was removed 
from this region and spread out on squared paper-. Table II shows 
the preliminary measurements made on the glass rod, and the surface area 
found from these measurements and from the film, respectively. 
TABLE II 
Measurements on Rod. 
Length . Diameter. 
(i) 3.05 cm. 0-493 cm. 
(ii) 3*07 >, °-497 „ 
(iii) 3-05 » 0-487 » 
Mean 3-06 „ 0-492 ,, 
Area of surface of Rod = 4*71 sq. cm. 
Area of Celluloidin Film = 4-80 ,, 
Error = 1.9% 
Using now the same solution of celluloidin and the same time of 
hardening the film (3 min.), this process was repeated, a shoot of Salicornia 
being substituted for the glass rod. The manipulation was more difficult 
in this case, owing to the delicate nature of the epidermis and the soft 
texture of the outer tissues ; the crevices at the nodes between the leaf 
segments and the stem also made it difficult to remove the film intact. 
However, after a few trials good films were obtained, and these gave areas 
sufficiently close to those obtained by calculation from measurements with 
the micrometer screw. 
Table III shows at A the measurements obtained from one such shoot 
of Salicornia , and at B the surface areas obtained by estimation from these 
figures and from the celluloidin film removed from the surface, and outlined 
in Fig. 6. 
