THE FLOWER. 
85 
it is the germinating ground of the pollen grains, it 
being viscid and especially adapted for this purpose. 
The stigmas may be separate, as in the Composite, or 
they may be united into a more or less club-shaped or 
globular head, consisting of as many lobes as there 
are stigmas, as in the poppy. The stigma, while 
usually solid, may have an opening, as in the violets, 
which sometimes has a lid-like appendage, as in Viola 
tricolor. 
The Ovules, as we have already seen, are small bodies 
which are borne on the placentae, and which, after fer- 
tilization, develop into seeds. The number of ovules 
varies considerably — there may be but one, as in the 
almond, or there may be a large number, as in the 
watermelon. A complete ovule consists of (1) a stalk ; 
(2) two coats — an outer and an inner ; (3) a narrow 
orifice for the entrance of the pollen tube, called the 
foramen; (4) a portion inclosed by the coats, known as 
the nucellus; (5) a more or less differentiated portion 
imbedded in the nucellus near the foramen, known as 
the embryo sac, and in which, after fertilization of the 
egg-cell, the embryo is formed. That portion of the 
ovule where the nucellus and coats grow together is 
known as the chalaza. 
There are several principal forms of ovules recognized, 
of which the following may be mentioned: (1) ortkotro- 
pous, in which the ovule is straight and erect on its stalk, 
as in the Urticacese; (2) anatropous, in which the 
ovule is bent over on to the stalk so as to be in an in- 
verted position, the line of attachment of the ovule and 
stalk being known as the raphe; most of the ovules of 
flowering plants belong to this group; (3) campylotro- 
pous, in which the ovule is bent upon itself, as in Stra- 
monium, this form being less frequent than the other 
two. 
