xiv INTRODUCTION TO BOTANY. — S 
base of the cavity, and either free at the top (free-central-placenta), or — 
attached also to the summit of the cavity. oa | 
parietal, when the ovules are attached to the inner surface or walls of the 
cavity of a one-celled compound ovary. Parietal placente are usually 
slightly thickened or raised lines ; sometimes broad surfaces nearly cover- — 
ing the inner surface of the cavity ; sometimes projecting far into the — 
cavity and constituting partial dissepiments, and even meeting in the — 
centre but without cohering there. In the latter case the distinction — 
between the one-celled and several-celled ovary sometimes almost dis- 
appears. | 
§ 12. The Ovule. 2 
117. The ovule is a minute body borne by the placenta (115) and destined, after — 
fertilization, to become the seed. At first it is merely a cellular excrescence, but asit 
enlarges it acquires a definite form and structure, and when fully grown consists of 
a central mass or nucleus, inclosed in one or two bag-like coats, the outer called pri- 
mine, the inner secundine. The nucleus is the essential part; in it the embryo is — 
formed after fertilization. The coats afterwards become the integuments of the seed. 
118. The chalaza is that point at which the base of the nucleus is confluent with 
the coats of the ovule, and is generally discoloured in the seed. The foramen is the 
common aperture of the coats, opposite the apex of the enclosed nucleus, and through 
which the pollen is admitted in fertilization : in the seed it is called the micropyle. — 
119. Ovules are said to be Ke :~ pe econ og ak Ga 
pasa 8 or straight (or atropous), when the chalaza or organic coin- 
cides with the West base of the ovule, and the foramen is situated 
at the opposite extremity, the ovule having a rectilinear axis : as in the 
Nettle, Dock, Fig, &c. : 
campylotropous or incurved, when, the base remaining the same, the axis is 
curved down and the foramen directed toward the base: as in the Caryo- 
phyllee and many leguminous plants. ‘: 
anatropous or inverted, when the chalaza, in an ovule with rectilinear axis, is_ 
- removed to the point most distant from the hilum, and the foramen 
brought close to the hilum. It is like an orthotropous ovule reversed on 
its cord ; the cord adhering to one side of the ovule and becoming more 
or less incorporated with its coats. Such an adhering cord, appearing 
either like a line or a ridge, is called the raphe: it connects the hilum 
with the chalaza. Anatropous ovules are much the commonest; good 
examples of distinctly marked raphe and chalaza may be found in the 
Orange and the Pansy. 
amphitrcpous or half-inverted, when the raphe extends but half the length of 
the ovule, and the chalaza and foramen, at opposite ends, are about equi- 
distant from the hilum: as in the Mallow-tribe, the Primrose, &c. 
$13. The Receptacle and relative attachment of the Floral Whorls. 
120. The Receptacle or torus is the extremity of the peduncle (above the calyx) 
upon which the corolla, stamens, and ovary, are inserted. It is sometimes little more 
than a mere point, but it is often more or less lengthened, thickened, or otherwise 
enlarged. term receptacle is also extended to the summit of a branch or inflo- 
rescence, On which the flowers of a head are inserted, as in the Composite.] 
121. A disk or disc is a circular enlargement of the receptacle, usually cup-shaped, — 
flat, or cushion-shaped (pulvinate), and often of a waxy or fleshy appearance. It is_ 
situated either immediately at the base of the ovary within the stamens, or between — 
pay ace and stamens, or bearing the petals or stamens or both at itsedge, or quite 
iP extremity of the receptacle, with the ovaries arranged in a ring round it or 
under it. : # 
122. The disk may be entire, toothed, lobed, or divided into a number of parts, 
usually as many or twice as many as the stamens or carpels. When the parts of 
divided disk are separate and short they are often called g — : 
123, Nectaries are either the disk, or small deformed petals, or abortive stamens, 
or appendages at the base of the petals, or stamens, or any small bodies within the 
