98 A GRAIN OF BARLEY. 
the styles to the conducting tissue of the upper part of the 
ovary, and growing down this and along the outer walls of 
the ovule, one of them finally enters the micropyle, and after 
piercing the wall of the embryo-sac mingles its contents with 
those of the oosphere, a cell situated at the apex of the 
embryo-sac. The act of fertilization is consequently exactly 
similar to the typical case I have already described. 
After fertilization great, and comparatively rapid, changes 
take place in both ovule and ovary, both of which increase 
very much in size, and become much more elongated in 
shape. 
First with regard to the embryo-sac. The fertilized oosphere 
commences to divide and sub-divide into a great number of 
cells which, in their collective form, ultimately become the 
embryo, whilst at the same time the other parts of the sac 
become filled with thin walled cells, filled with protoplasm, 
out of which starch granules are slowly elaborated. These 
starch-containing cells constitute the greater part of the con- 
tents of the embryo-sac, but on the inner wall of the sac, 
and external to these starch-containing cells, is a triple row 
of rectangular cells with granulated contents. The starch-con- 
taining cells, and the rectangular cells, together constitute the 
endosperm, the white mealy looking substance which constitutes 
by far the greater portion of the barley grain. We see, there- 
fore, that by far the most important portions of the barley 
grain, the white floury endosperm, and the embryo, doth 
originate in the embryo-sac, and if we follow the development 
of this sac, from the period immediately subsequent to fertili- 
zation, to the full ripening of the grain, we find it gradually 
increasing at the expense of all other parts. First of all 
during its enlargement, it gradually displaces the whole of the 
nucleus, with the exception of the merest remnant. The 
inner integument of the ovule is also absorbed, and the 
thin retaining wall of the embryo-sac becomes firmly united 
with the outer integument of the ovule. I have mentioned 
that during the ripening of the seeds of many fruits, eg., 
