: SURFACE OF THE OVARY.—PLACENTATION. 231 
tions, which then give a somewhat angular appearance to the 
ovary. 
The epidermis covering the surface of the ovary may be either 
perfectly smooth, or furnished in various ways with different 
kinds of hairs ; or it may assume a glandular appearance. In 
these cases the same terms are used as in describing similar 
conditions of the surface of the leaves, or of the other organs 
of the plant. 
When the ovary is compound, the number of carpels of which 
it is composed may be ascertained in one or more of the follow- 
ing ways. Thus, when the styles (jig. 464), or stigmas (jig. 32), 
remain distinct, the number of these generally corresponds to the 
number of carpels. It does, however, occasionally happen, as in 
Euphorbia (fig. 627), that the styles are themselves divided, in 
which case they would of course indicate a greater number of 
carpels than are actually present ; we must then resort to other 
modes of ascertaining this point, such, for instance, as the fur- 
Fic. 627. Fic. 628, 
Fig. 627. Pistillate flower of a species of Euphorbia, with three forked styles. 
—Fig. 628. Vertical section of the flower of the Stonecrop. pi. Placenta 
of one of the ovaries arising from the ventral suture. 
rows or lobes on the external surface of the ovary; or the 
number of partitions or loculi which it contains, as these com- 
monly correspond in number to the carpels of which that ovary 
is composed. The mode of venation may in some cases also 
form a guide in the determination ; while in others the manner 
in which the ovules are attached must be taken into considera- 
tion. We now pass to the examination of the latter point. 
Placentation.—The term placenta is commonly applied to the 
more or less marked projection occurring in the cavity of the ovary 
(figs. 585, p, and 628, pl), to which the ovule or ovules are 
attached. The placentas are variously distributed in the ovaries 
of different plants, but their arrangement is always the same for 
that of any particular species, and frequently throughout entire 
genera, or even natural orders ; hence their accurate discrimi- 
nation is of great practical importance (see page 286). The 
term placentation is used to indicate the manner in which the 
placentas are distributed. The placenta is called by Schleiden 
the spermophore. 
