104 A GRAIN OF BARLEY. 
other plants or on the products of their decay, from which 
they absorb the organic carbon compounds which in the first 
instance have been assimilated from the air by the green parts 
of the plants which form their host. 
A plant which thus obtains its nourishment from a living 
host is called a jarasite, whilst, if it flourishes on the host 
when dead and decaying, we call it a saprophyte. 
The young embryo of the barley seed does not contain any 
chlorophyll, and even if it did it would be no use to it as 
long as the grain was buried in the ground beyond the influ- 
ence of light. Under these circumstances the embryo, in its 
early stages of growth, in fact until it has produced green 
leaves above the ground, /eads the life of a true parasitic 
plant. Its host is the endosperm, with its contents of starch 
cellulose and proteids, and from this reservoir of material 
the young plant draws its supplies, until, by the time they 
are exhausted, its green leaves are able to assimilate for 
themselves. 
I cannot too strongly emphasize the fact of the parasitic 
nature of the embryo, as this enables us better to understand 
its subsequent development. The connection between the 
embryo and the endosperm is not so close as that between 
many parasites and their host. As [ have said before, we find 
nothing approaching to an organic connection between the 
two, and there are no processes or prolongations of the tissue 
of one into the other. We find that the embryo can be 
dissected out from the mealy endosperm without rupturing 
the tissue of either, and that the position of the two with 
regard to each other is only one of very close and intimate 
apposition. This is well shewn in the photo-micrograph, 
Fig. 10, Plate IV. 
Turning to the large longitudinal section of the grain, and 
also to the photograph just referred to, we see that the limit- 
ing surface of the embryo, which is turned towards the centre 
of the grain, is a layer of palisade-like cells, set at right 
angles to the surface, and forming a well-marked eithelium. 
