382 Collins.—The Structure of the Integumentary System of the 
Rarely do seeds possess an investment of so complex a nature, and 
there can be no doubt that it is biologically significant; yet an exploration 
of the literature dealing with the barley grain showed that no account of 
the integumentary system was readily accessible, and that the details of its 
structure and development were very little known. 
Holzner and Lermer ( 1 ), in their classic account of the barley grain, 
dealt in some detail with its structure, and the interpretation put upon the 
structure was adopted very largely by Horace Brown and Morris (2) in 
their splendid work on the histological and physiological changes which 
occur at the germination of the grain. 
More recently, Adrian Brown’s ( 3 ) fascinating series of experiments 
has focused interest on the integumentary system as the seat of semi- 
permeable properties. The discovery was made when grains of Hordeum 
vulgare var. caendescens were steeped in sulphuric acid. This particular 
variety lends itself to an ocular demonstration of the phenomenon, because, 
if the integumentary system is imperfect, the sulphuric acid enters the grain 
and the blue pigment contained in the aleurone layers is reddened, whereas 
grains in which the membrane is perfect swell, but do not show the colour 
change. More than ordinary interest is attached to this discovery, because 
it was the first instance of an efficient natural non-living membrane of 
this type. 
From the experimental evidence obtained, Brown assumed that the 
property resided in the nucellar epidermis, and that water and penetrant 
substances like iodine entered generally and uniformly all over its surface 
excepting the flanks of the furrow, where the entry of iodine was delayed. 
During the course of the publication of Brown’s papers, other workers 
investigated the phenomenon of semi-permeability in seeds. Amongst 
these may be mentioned Schroeder ( 4 ), Atkins ( 5 ), Reichard (6), and 
Shull ( 7 ). 
Schroeder, investigating the phenomenon in wheat, showed that a con¬ 
centration of the solution occurred when grains were immersed in a solution 
of salt. He endeavoured to correlate the weight increase of the grain with 
the calculated increase of weight from the increased titre due to the uptake 
of water by the grain. It will readily be seen that an exact result cannot 
be expected, for the grain-coverings will increase in weight by the uptake 
of the salt solution, whilst a number of damaged grains must be allowed 
for. It is not surprising, therefore, that the actual weight increase was con¬ 
siderably higher than that calculated from the increased concentration of 
the solution, which of itself indicates penetration of the grain. Further 
experiments showed that a solution of silver nitrate in 50 per cent, alcohol 
penetrated the grain, as did osmic acid and iodine in solution, the two 
latter proceeding from the basal or proximal end, as indicated by the colour 
change. Watery solutions of chloroform and ether accelerated the uptake 
