Chapter XXI: 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”).

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 the hickory (Fig. 225), and the 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.)

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.

A 1-loculed pericarp which dehisces along the front edge (that is, the inner edge, next the centre 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.

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_.

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.

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.

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.

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_.

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 the 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 the 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 the 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.

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.

=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 stem was it attached? Are there
any remains of the blossom at the blossom end? Describe texture and
colour 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 sub-divided?
What is the number of seeds? Are the seeds free, attached to
the wall of the vessel, or to a support in the centre? 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 fruit
can you buy in the market, and to what groups or classes do they
belong? Of which fruits 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. Colour. 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?

NOTE TO TEACHER.—There are few more interesting subjects to
beginning pupils than fruits,—the pods of many kinds, forms, and
colours, 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. 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._