A GRAIN OF BARLEY. 97 
producing a leverage action, which tends to draw the palez 
slightly apart at their apex. 
The ovary of barley before fertilization is a very small 
object, scarcely exceeding in size the head of a moderate- 
sized pin. It is not particularly easy to make sections 
through it which will exhibit its structure, but with care and 
patience this can be done. Plate III. exhibits the principal 
points which are brought out by the examination under a high 
magnifying power of its longitudinal and transverse sections. 
You see that the ovary is mainly composed of soft, thin- 
walled tissue, or parenchyma (see description of Plates at end) 
as it is called, enclosing a solitary ovule with double envelopes. 
The interior of this ovule is the muclews, and, just as in the 
typical flower which I described a little time ago, we find that 
one cell of this nucleus is very much larger than the others 
—this is the emdryo-sac. Observe the canal-like opening, the 
micropyle, at the apex of the ovule, with the embryo-sac 
extending almost into its mouth. The ovule is inverted, its 
apex, marked by the micropyle, pointing downward, as in the 
typical case we considered; it is consequently anatropous. 
The attachment of the ovule to the ovary claims our special 
attention. You will see, by an examination of the two sections, 
that the ovule lies perfectly free within the cavity of the 
ovary, except along a narrow line on the ventral side. This 
line represents the fwmicle or attachment of the ovule to the 
inner walls of the ovary. The thick walls of the ovary itself 
are almost colourless except in one layer, which is coloured 
bright green. The cells of this layer contain a considerable 
amount of chlorophyll, the remarkable substance which gives 
the green colour to foliage leaves, and enables the plant to 
assimilate food from the carbonic acid of the air. 
When the pollen grains are shed by the anthers, and 
come into contact with the hairy stigmas with which the 
upper part of the ovary is furnished, one of which is depicted 
in Plate III., Fig. 9, the minute tubes which are extended 
from ie pollen-grains find their way along the substance of 
