FRUITS
The ripened ovary, with its attachments, is known as the =fruit=.
_It contains the seeds._ If the pistil is simple, or of one carpel,
the fruit also will have one compartment. If the pistil is compound,
or of more than one carpel, the fruit usually has an equal number
of compartments. The compartments in pistil and fruit are known as
=locules= (from Latin _locus_, meaning “a place”).
[Illustration: FIG. 224.--DENTARIA, OR TOOTH-WORT, in fruit.]
The simplest kind of fruit is a _ripened 1-loculed ovary_. The first
stage in complexity is a ripened _2- or many-loculed ovary_. Very
complex forms may arise by the _attachment of other parts to the
ovary_. Sometimes the style persists and becomes a beak (mustard pods,
dentaria, Fig. 224), or a tail as in clematis; or the calyx may be
attached to the ovary; or the ovary may be embedded in the receptacle,
and ovary and receptacle together constitute the fruit: or an involucre
may become a part of the fruit, as possibly in the walnut and hickory
(Fig. 225), and cup of the acorn (Fig. 226). The chestnut and the beech
bear a prickly involucre, but the nuts, or true fruits, are not grown
fast to it, and the involucre can scarcely be called a part of the
fruit. A ripened ovary is a =pericarp=. A pericarp to which other parts
adhere has been called an accessory or reënforced fruit. (Page 169.)
[Illustration: FIG. 225.--HICKORY-NUT. The nut is the fruit, contained
in a husk.]
[Illustration: FIG. 226.--LIVE-OAK ACORN. The fruit is the “seed” part;
the involucre is the “cup.”]
[Illustration: FIG. 227.--KEY OF SUGAR MAPLE.]
[Illustration: FIG. 228.--KEY OF COMMON AMERICAN ELM.]
Some fruits are =dehiscent=, or split open at maturity and liberate the
seeds; others are =indehiscent=, or do not open. A dehiscent pericarp
is called a =pod=. The parts into which such a pod breaks or splits
are known as =valves=. In indehiscent fruits the seed is liberated by
the decay of the envelope, or by the rupturing of the envelope by the
germinating seed. Indehiscent winged pericarps are known as =samaras=
or =key fruits=. Maple (Fig. 227), elm (Fig. 228), and ash (Fig. 93)
are examples.
=Pericarps.=--The simplest pericarp is a dry, one-seeded, indehiscent
body. It is known as an =akene=. A head of akenes is shown in Fig.
229, and the structure is explained in Fig. 230. Akenes may be seen in
buttercup, hepatica, anemone, smartweed, buckwheat.
[Illustration: FIG. 229.--AKENES OF BUTTERCUP.]
[Illustration: FIG. 230.--AKENES OF BUTTERCUP, one in longitudinal
section.]
A 1-loculed pericarp which dehisces along the front edge (that is, the
inner edge, next the center of the flower) is a =follicle=. The fruit
of the larkspur (Fig. 231) is a follicle. There are usually five of
these fruits (sometimes three or four) in each larkspur flower, each
pistil ripening into a follicle. If these pistils were united, a single
compound pistil would be formed. Columbine, peony, ninebark, milkweed,
also have follicles.
[Illustration: FIG. 231.--FOLLICLE OF LARKSPUR.]
[Illustration: FIG. 233.--CAPSULE OF CASTOR-OIL BEAN AFTER DEHISCENCE.]
[Illustration: FIG. 232.--A BEAN POD.]
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.
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, wallflower, 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.]
The pericarp may be _fleshy and indehiscent_. A pulpy pericarp
with several or many seeds is a =berry= (Figs. 239, 240, 241). To
the horticulturist a berry is a small, soft, edible fruit, without
particular reference to its structure. The botanical and horticultural
conceptions of a berry are, therefore, unlike. In the botanical sense,
gooseberries, currants, grapes, tomatoes, potato-balls, and even
eggplant fruits and oranges (Fig. 241) are berries; strawberries,
raspberries, blackberries are not.
[Illustration: FIG. 242.--PLUM; example of a drupe.]
A fleshy pericarp containing one relatively large seed or stone is a
=drupe=. Examples are plum (Fig. 242), peach, cherry, apricot, olive.
The walls of the pit in the plum, peach, and cherry are formed from the
inner coats of the ovary, and the flesh from the outer coats. Drupes
are also known as _stone-fruits_.
[Illustration: FIG. 243.--FRUIT OF RASPBERRY.]
[Illustration: FIG. 244.--AGGREGATE FRUIT OF MULBERRY; and a separate
fruit.]
Fruits that are formed by the subsequent union of separate pistils are
=aggregate fruits=. The carpels in aggregate fruits are usually more or
less fleshy. In the raspberry and blackberry flower, the pistils are
essentially distinct, but as the pistils ripen they cohere and form one
body (Figs. 243, 244). Each of the carpels or pistils in the raspberry
and blackberry is a little drupe, or =drupelet=. In the raspberry the
entire fruit separates from the torus, leaving the torus on the plant.
In the blackberry and dewberry the fruit adheres to the torus, and the
two are removed together when the fruit is picked.
=Accessory Fruits.=--When the pericarp and some other part grow
together, the fruit is said to be =accessory= or =reënforced=. An
example is the strawberry (Fig. 245). The edible part is a greatly
_enlarged torus_, and the pericarps are akenes embedded in it. These
akenes are commonly called seeds.
[Illustration: FIG. 245.--STRAWBERRY; fleshy torus in which akenes are
embedded.]
Various kinds of reënforced fruits have received special names. One of
these is the =hip=, characteristic of roses. In this case, the torus is
deep and hollow, like an urn, and the separate akenes are borne inside
it. The mouth of the receptacle may close, and the walls sometimes
become fleshy; the fruit may then be mistaken for a berry. The fruit of
the pear, apple, and quince is known as a =pome=. In this case the five
united carpels are completely buried in the hollow torus, and the torus
makes most of the edible part of the ripe fruit, while the pistils are
represented by the core (Fig. 246). Observe the sepals on the top of
the torus (apex of the fruit) in Fig. 246. Note the outlines of the
embedded pericarp in Fig. 247.
[Illustration: FIG. 246.--SECTION OF AN APPLE.]
[Illustration: FIG. 247.--CROSS-SECTION OF AN APPLE.]
=Gymnospermous Fruits.=--In pine, spruces, and their kin, there is no
fruit in the sense in which the word is used in the preceding pages,
because _there is no ovary_. The ovules are naked or uncovered, in the
axils of the scales of the young cone, and they have neither style nor
stigma. The pollen falls directly on the mouth of the ovule. The ovule
ripens into a seed, which is usually winged. Because the ovule is not
borne in a sac or ovary, these plants are called =gymnosperms= (Greek
for “naked seeds”). All the true cone-bearing plants are of this class;
also certain other plants, as red cedar, juniper, yew. The plants are
monœcious or sometimes diœcious. The staminate flowers are mere naked
stamens borne beneath scales, in small yellow catkins which soon fall.
The pistillate flowers are naked ovules beneath scales on cones that
persist (Fig. 29). Gymnospermous seeds may have several cotyledons.
SUGGESTIONS.--=168.= Study the following fruits, or any five fruits
chosen by the teacher, and answer the questions for each: Apple,
peach, bean, tomato, pumpkin. What is its form? Locate the scar left
by the stem. By what kind of a stem was it attached? Is there any
remains of the blossom at the blossom end? Describe texture and color
of surface. Divide the fruit into the seed vessel and the surrounding
part. Has the fruit any pulp or flesh? Is it within or without the
seed vessel? Is the seed vessel simple or subdivided? What is the
number of seeds? Are the seeds free, attached to the wall of the
vessel, or to a support in the center? Are they arranged in any
order? What kind of wall has the seed vessel? What is the difference
between a peach stone and a peach seed? =169.= The nut fruits
are always available for study. Note the points suggested above.
Determine what the meat or edible part represents, whether cotyledons
or not. Figure 248 is suggestive. =170.= Mention all the fleshy
fruits you know, tell where they come from, and refer them to their
proper groups. =171.= What kinds of fruits can you buy in the market,
and to what groups or classes do they belong? Of which ones are the
seeds only, and not the pericarps, eaten? =172.= An ear of corn is
always available for study. What is it--a fruit or a collection of
fruits? How are the grains arranged on the cob? How many rows do you
count on each of several ears? Are all the rows on an ear equally
close together? Do you find an ear with an odd number of rows? How
do the parts of the husk overlap? Does the husk serve as protection
from rain? Can birds pick out the grains? How do insect enemies enter
the ear? How and when do weevils lay eggs on corn? =173.= _Study a
grain of corn._ Is it a seed? Describe the shape of a grain. Color.
Size. Does its surface show any projections or depressions? Is the
seed-coat thin or thick? Transparent or opaque? Locate the hilum.
Where is the silk scar? What is the silk? Sketch the grain from the
two points of view that show it best. Where is the embryo? Does the
grain have endosperm? What is dent corn? Flint corn? How many kinds
of corn do you know? For what are they used?
[Illustration: FIG. 248.--PECAN FRUIT.]
NOTE TO TEACHER.--There are few more interesting subjects to
beginning pupils than fruits,--the pods of many kinds, forms, and
colors, the berries, and nuts. This interest may well be utilized
to make the teaching alive. All common edible fruits of orchard and
vegetable garden should be brought into this discussion (some of
the kinds are explained in “Lessons with Plants”). Of dry fruits,
as pods, burs, nuts, collections may be made for the school museum.
Fully mature fruits are best for study, particularly if it is desired
to see dehiscence. For comparison, pistils and partially grown fruits
should be had at the same time. If the fruits are not ripe enough to
dehisce, they may be placed in the sun to dry. In the school it is
well to have a collection of fruits for study. The specimens may be
kept in glass jars. _Always note exterior of fruit and its parts:
interior of fruit with arrangement and attachment of contents._