A 1-loculed pericarp that dehisces on both edges is a =legume=. Peas
and beans are typical examples (Fig. 232); in fact, this character
gives name to the pea family,—Leguminosæ. Often the valves of the
legume twist forcibly and expel the seeds, throwing them some
distance. The word “pod” is sometimes restricted to legumes, but it
is better to use it generically for all dehiscent pericarps.
[Illustration: FIG. 233.—CAPSULE OF CASTOR-OIL BEAN AFTER DEHISCENCE. ]
A compound pod—dehiscing pericarp of two or more carpels—is a
=capsule= (Figs. 233, 234, 236, 237). Some capsules are of one
locule, but they may have been compound when young (in the ovary
stage) and the partitions may have vanished. Sometimes one or more
of the carpels are uniformly crowded out by the exclusive growth of
other carpels (Fig. 235). The seeds or parts which are crowded out
are said to be _aborted_.
[Illustration: FIG. 234.—CAPSULE OF MORNING GLORY.]
[Illustration: FIG. 235.—THREE-CARPELED FRUIT OF HORSE-CHESTNUT. Two
locules are closing by abortion of the ovules. ]
There are several ways in which capsules dehisce or open. When
they break _along the partitions_ (or septa), the mode is known as
=septicidal dehiscence= (Fig. 236); In septicidal dehiscence the
fruit separates into parts representing the original carpels. These
carpels may still be entire, and they then dehisce individually,
usually along the inner edge as if they were follicles. When the
compartments _split in the middle, between the partitions_, the mode
is =loculicidal dehiscence= (Fig. 237). In some cases the dehiscence
is _at the top_, when it is said to be =apical= (although several
modes of dehiscence are here included). When the _whole top comes
off_, as in purslane and garden portulaca (Fig. 238), the pod is
known as a =pyxis=. In some cases apical dehiscence is by means of a
hole or clefts.
[Illustration: FIG. 236.—ST. JOHN’S WORT. Septicidal.]
[Illustration: FIG. 237.—LOCULICIDAL POD OF DAY-LILY.]
The peculiar capsule of the mustard family, or Cruciferæ, is known
as a =silique= when it is distinctly longer than broad (Fig. 224),
and a =silicle= when its breadth nearly equals or exceeds its length.
A cruciferous capsule is 2-carpeled, with a thin partition, each
locule containing seeds in two rows. The two valves detach from
below upwards. Cabbage, turnip, mustard, water-cress, radish, rape,
shepherd’s purse, sweet alyssum, wall-flower, honesty, are examples.
[Illustration: FIG. 238.—PYXIS OF PORTULACA OR ROSE-MOSS.]
[Illustration: FIG. 239.—BERRIES OF GOOSEBERRY. Remains of calyx at
_c_.]
[Illustration: FIG. 240.—BERRY OF THE GROUND CHERRY OR HUSK TOMATO,
contained in the inflated calyx. ]
[Illustration: FIG. 241.—ORANGE; example of a berry.]
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