INTRODUCTION TO BOTANY. Xvi 
§ 13. The Ovule. 
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 as it enlarges it acquires a definite form and 
structure, and when fully grown consists of a central mass or nucleus, en- 
closed in one or two bag-like coats, the outer called primine, 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 chaldaza is that point at which the base of the nucleus is con- 
fluent 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 fertiliza- 
tion: in the seed it is called the micropyle. 
119. Ovules are said to be, 
orthotropous or straight (or atropous), when the chalaza or organic 
base coincides with the apparent 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, etc. 
campylotropous or incurved, when, the base remaining the same, the 
axis is curved down and the foramen directed towards the base ; 
as in the Caryophylice and many leguminous plants. 
anatropous or inverted, when the chalaza, in an ovule with rec- 
tilmear 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. 
amphitropous or half-inverted, when the raphe extends but half the 
length of the ovule, and the chalaza and foramen, at opposite 
ends, are about equidistant from the hilum: as in the Mallow 
tribe, the Primrose, ete. 
§ 14. 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. [The term receptacle is also 
extended to the summit of a branch or inflorescence, 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 the petals and stamens, or bearing 
the petals or stamens or both at its edge, or quite at the 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 a divided disk are separate and short, they are often called 
lands. 
123. Nectaries are either the disk, or small deformed petals, or abortive 
, 
