On the Existence of a Semi*permeable Membrane 
enclosing the Seeds of some of the Gramineae. 
BY 
ADRIAN J. BROWN. 
D URING a recent investigation of the conditions governing the absorp- 
tion of water by the ripe grain of certain cereals, some experiments 
with the grain of Hordeum vulgare , var. caerulescens , indicated that the 
embryo and endosperm of the grain are contained within a semi-permeable 
covering. 
The grain of this variety of H. vulgare is characterized by a greenish- 
blue colour, due to the presence of a blue pigment in its aleurone cells. 
As the colour of this pigment, like litmus, is changed to red by acid, the 
grain is therefore naturally furnished with an indicator by means of which 
the access of free acid to its aleurone cells may be detected. 
During some experiments with the blue variety of H. vulgare , in which 
the grain was steeped in a dilute solution (i per cent.) of sulphuric acid, it was 
noticed that when the skins of the grain were punctured or otherwise 
damaged the colour of the aleurone cells of the grain adjacent to the 
damaged part of the skin rapidly changed to red, and that this colour 
transformation gradually spread to all the cells of the aleurone layer, 
demonstrating diffusion of acid throughout the endosperm of the grain. 
When, however, undamaged grain of the same variety of barley was 
steeped in a similar solution of acid it was observed that although the 
contents of the grain became soft and swollen from absorption of water, 
the aleurone cells retained their original blue colour, indicating that the 
acid had not obtained access to the interior of the grain. It was further 
noticed that this condition remained for a week or even longer, if germination 
of the grain was prevented or delayed by keeping it submerged in the acid 
steeping liquid. If, however, germination took place, with consequent 
rupture by the growing roots of the skins of the grain where they protect 
the base of the embryo, the aleurone cells of the grain speedily changed to 
a red colour, indicating that acid had diffused through the tissues of the 
embryo into the endosperm of the seed. 
[Annals of Botany, Vol. XXI. No. LXXXI. January, 1907.] 
