398 Collins .— The Structure of the Integumentary System of the 
mouth was covered by the flange of the tube. After four months the 
height attained in the osmometer tube was 20-6 cm. and traces of salt were 
found in the chloroform water. Iodine was now added to the chloroform 
water and in a few days a layer of starch attached to the membrane was 
coloured blue. Five months from the commencement of the experiment 
the height reached in the tube was 27-2 cm.; about one-half of the whole 
starch layer had been coloured by the iodine. 
At the time the experiment was planned it was thought desirable to 
see whether an isolated portion of the grain-covering could be used to 
demonstrate semi-permeability. Moreover, if the result was satisfactory, 
a useful comparison between the rate of passage of water across the barley 
septum used in the osmometer tube and the rate of the uptake of water 
by barley when steeped could be made. From this point of view the 
results were not satisfactory, for the calculations made revealed the fact that 
the rate at which water passed across the septum was continually accelerated 
notwithstanding the accompanying dilution of the salt solution, and it was 
evident that, owing to some alteration, the membrane became more and 
more permeable as the experiment progressed. It must be recalled that, 
although the grain had been steeped 12 hours before the septum was cut 
from it and fixed, no rise in the level of the salt solution was evident for 
the first five days of the experiment, a fact in harmony with the theory 
advanced in this paper, that the cuticularization of the tegmen prevents 
the immediate absorption of water over the general surface of the grain. 
(d) Efficiency of the superficial structures of the grain in capillary 
conduction of liquids. 
If the apex of the grain dips into water or other liquid, the liquid 
quickly travels to the germinal end. The outer paleae are very efficient 
capillary conductors, and act so because of the porous character of the 
thin-walled tissue beneath the fibrous sub-epidermal cells, the openings in 
the epidermis being accessory to this function. When the apex of the 
grain is touched with a drop of coloured alcoholic solution, the colouring 
is seen to spread towards the germ end with surprising rapidity. The 
paths principally taken are the furrow and the overlapping edges of the 
inferior palea. The furrow, wide at its apical end, narrows and deepens 
quickly towards the germinal end, where it is roofed by the hairy rachilla, 
and is thus built on a plan suitable for the rapid conveyance of liquid. The 
whole integumentary system seems admirably adapted for the absorption 
and conduction of water to the point where it most readily finds admittance 
to the seed. 
To obtain some idea of the efficiency of this conducting mechanism, 
the relative uptake of water by (a) grains wholly immersed, (fi) grains 
whose*germinal end just dipped into water, (e) grains whose apex just 
