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”).

[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._