enclosing the Seeds of some of the Gramineae . 85 
were ruptured. In the case of the grains boiled for 30, 10, and 5 minutes 
all remained whole. 
Following on the treatment with boiling water the grains from the 
three last experiments, the skins of which were apparently uninjured, were 
steeped in normal sulphuric acid for 48 hours. On subsequent examination 
it was found that no trace of acid had penetrated to the interior of the 
grains except in a very few instances in which the skins of the grains had 
been accidentally damaged. In order to obtain additional evidence that life 
in the grains had been destroyed by the treatment to which they had been 
subjected, some of the grains which had been immersed in boiling water 
for the shortest period of time (5 minutes) were placed under conditions 
favourable to germination, with the result that they exhibited no signs of 
life. 
The above experiments therefore show conclusively that the semi- 
permeable property of the envelope of the barley grain is not a function of 
living protoplasm. 
A study of the nature and position of the semi-permeable envelope 
enclosing the barley grain was then commenced. Previous observations 
regarding the behaviour of the blue pigment in the aleurone cells of grains 
of H. vulgare , var. caerulescens , when steeped in an acid solution, demon- 
strate that the semi-permeable envelope must occupy a position which is 
external to the aleurone cells of the endosperm, and also that it must 
enclose both the embryo and endosperm of the grain. 
The envelope enclosing the embryo and endosperm of the barley grain 
apparently consists 1 : (1) of the pales, originally the floral envelope ; (2) of 
the pericarp, composed of several layers derived from the component parts 
of the walls of the ovary ; and (3) of the spermoderm, composed of the 
ovular integuments together with the outer layer of the nucellar tissue. 
The semi-permeable property of the grain therefore should be located in 
one or more of these coverings. 
The pales of the grain do not function as the semi-permeable covering, 
for after their removal the grain exhibits its semi-permeable property 
equally as well as before. The property also does not appear to be 
a function of any part of the pericarp, for the layers of cells composing 
this covering are disintegrated when the barley grain is digested in 
a 36 per cent, solution of sulphuric acid without the semi-permeability of 
the grain being destroyed. (See above, p. 81.) 
The spermoderm of the grain, however, resists the action of 36 per cent, 
sulphuric acid in a very remarkable manner, and hence this covering or one 
of its component layers probably constitutes the semi-permeable membrane 
of the barley grain. 
1 See 4 Developpement et constitution de l’endosperme de l’orge ’. W. Johannsen. Comptes 
Rendus des travaux du Laboratoire de Carlsberg. Vol. 2, 1884, 63. 
