390 Collins— The Structure of the Integumentary System of the 
Section III. Location of the Uptake of Water by the 
Barley Grain. 
(a) General . 
The possession of such a strongly cuticularized tegmen membrane 
as has been shown to envelop the grain is very striking. That cuticle 
is to a certain very small extent permeable to water is established, for 
cuticular transpiration is a well-recognized phenomenon, and it has been 
shown that if potassium nitrate is placed on a moistened and wetted area 
of the cork layer covering the potato* a little water is slowly absorbed from 
the potato. On the other hand, both cuticle and cork are quite imperme¬ 
able to many substances. The cuticle of the onion, for example, is 
impermeable to potassium nitrate, copper sulphate, and mercuric chloride. 
A few experiments w r ere made to see how far the cuticle of the upper 
surface of the leaf of the cherry laurel was permeable. Pieces of the leaf 
were sealed by wax of low melting-point across the mouth of conical tubes 
with flanged and ground ends, so that the cuticular surface was exposed to 
solutions put into the tubes. After exposure to the solution for some days, 
sections of that part of the leaf exposed to its action were made and 
examined, but no evidence of penetration was found. In this way resistance 
to penetration of strong solutions of iodine and trichloracetic acid was 
determined. Armstrong ( 9 ) had previously demonstrated that cuticle was 
impermeable to solutions of cadmium iodide, acetic acid, and mercuric 
chloride, amongst other substances, and yet all these substances were found 
by Brown to penetrate the barley grain. 
It is interesting in this connexion to recall the fact of the relatively 
slow uptake of water by the barley grain, since some six or seven days 
may elapse before it comes to a maximum weight when steeped in water, 
whilst split grains reach a similar weight in about thirty-six hours. 
From this evidence it was thought possible that there was no marked 
general permeation of the cuticular investment, and that penetration 
occurred only at certain spots, and some preliminary experiments were 
made to test this view. A number of grains was placed in a beaker of dis¬ 
tilled water at ordinary laboratory temperature. Every three hours grains 
were removed from the water, dried carefully, placed between pieces of 
cork, and cut across the mid region with a dry razor. The cut surface 
of the grain, which was still held between the pieces of cork, was pressed 
down upon a piece of dried cobalt paper. The result, after nine hours’ 
immersion, was a print with a pink outline of the grain and a large blue 
interior. Some measurements were taken of the diameter of the blue 
centre and the thickness of the pink rim with a millimetre scale, but they 
are not claimed to be more than rough measurements. Whole grain : 
4 mm. x 3 mm. Blue centre: 3-75 mm. x 2*5 mm. Tests were made 
between nine and twenty-four hours, and grains were obtained, after twenty 
