106 THE FLOWERING PLANT. 
primrose will show that there is a single cavity into which a 
knob-like placenta projects, upon which numerous ovules are 
situated. his kind of placentation is free central. ‘The presence 
of two styles points to two carpels, but in primrose the pistil is 
from the first absolutely devoid of branching or lobation. Is it 
then a single carpel? If so, it would naturally have a ventral 
suture, and be bilaterally symmetrical, as is the case in the pea. 
But the pistil of primrose is absolutely terminal and radially 
symmetrical ; and in thrift, a plant belonging to a closely related 
family, the flowers agree very nearly with those of primrose, 
excepting only that five styles are present. A great deal of 
discussion has arisen as to the nature of the knob-like placenta 
in the primrose and other forms. Some regard it as the dilated 
end of the axis. If so, the placentation is axial, ¢.e., the ovules 
are borne by the axis, and not by the carpels. (JV.B.—Do not 
confound this term with axle.) But the knob may very possibly 
be more or less formed from the carpels. It is best, for the 
present, to keep the word free-central, as that simply refers to 
the way of arrangement. There are other cases in which the 
ovules are, or appear to be, developed on the axis. Jn docks, for 
instance, a single ovule grows straight up from the bottom of the 
unilocular ovary, apparently forming the end of the axis. The 
florets of daisy, dandelion, sunflower, &c., present a seed-like 
structure beneath the coloured corolla. This is the inferior ovary. 
Although there are two cohering carpels, as shown (fig. 43) by 
the forked style (cf. p. 100), the ovary contains but one cavity, 
from the base of which a single ovule rises. Just by the side of 
it is a minute knob. This represents the end of the axis, upon 
the side of which the ovule appears to be borne. 
An ovule may take various directions. .When growing up 
from the bottom of a loculus, it is erect, as in dock. An ovule 
developed on the side of a loculus is very frequently horizontal, as 
in lily. Advantage is taken of this fact in procuring longitudinal 
sections of the ovules, 7.e., transverse sections of the ovary are 
made. Or such an ovule may be directed upwards, ascending, é.9., 
buttercup, or hanging downwards, pendulous, as in rose. If it 
hangs down from the top of the loculus, it is suspended. Anemone 
is an instance. When one or a few ovules only are present, more 
attention is paid to their direction than when a large number exist. 
Nectaries may be situated on the pistil. The best example of 
this is found in inferior ovaries, upon the top of which a fleshy 
honey-secreting cushion, commonly called the disc, is often pre- 
sent. Parsnip, hemlock, and daisy are good examples. The 
nectary of dead nettle is a fleshy outgrowth from the front of the 
ovary. 
