FRUIT IDENTIFICATION LABORATORY
The term fruit has different meanings depending on context. In botany, a fruit is the ripened
ovary—together with seeds—of a flowering plant. In many species, the fruit incorporates the
ripened ovary and surrounding tissues. Fruits are the means by which flowering plants
disseminate seeds. In cuisine, when discussing fruit as food, the term usually refers to those plant
fruits that are sweet and fleshy, examples of which include plums, apples and oranges. However,
a great many common vegetables, as well as nuts and grains, are the fruit of the plant species
they come from.
A fruit is a ripened ovary. After the ovule in an ovary is fertilized in a process known as
pollination, the ovary begins to ripen. The ovule develops into a seed and the ovary wall pericarp
may become fleshy (as in berries or drupes), or form a hard outer covering (as in nuts). In some
cases, the sepals, petals and/or stamens and style of the flower fall off. Fruit development
continues until the seeds have matured. With some multiseeded fruits the extent to which the
flesh develops is proportional to the number of fertilized ovules.
The wall of the fruit, developed from the ovary wall of the flower, is called the pericarp. The
pericarp is often differentiated into two or three distinct layers called the exocarp (outer layer also called epicarp), mesocarp (middle layer), and endocarp (inner layer). In some fruits,
especially simple fruits derived from an inferior ovary, other parts of the flower (such as the
floral tube, including the petals, sepals, and stamens), fuse with the ovary and ripen with it. The
plant hormone ethylene causes ripening. When such other floral parts are a significant part of the
fruit, it is called an accessory fruit. Since other parts of the flower may contribute to the structure
of the fruit, it is important to study flower structure to understand how a particular fruit forms.
The internal structure of a flower consists of 4
whorls:
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


Sepals (collectively called calyx)
Petals (collectively called corolla)
Stamens (the male part)
Carpel or Pistil (the female part)
A carpel is the female reproductive organ of a flower; the basic unit of the gynoecium. The parts
of the carpel are:



the stigma (plural: stigmas), usually the terminal (end) portion that has no epidermis and
is fitted to receive pollen (male gametes); it is commonly somewhat glutinous or viscid;
the style, a stalk connecting the stigma with the ovary below containing the transmitting
tract, which facilitates the movement of the male gamete to the ovule; and
the ovary (also called a megasporophyll) containing the female reproductive cell or
ovule.
The carpel (if single) or carpels (if fused) comprise the pistil of the flower. A flower with two or
more fused carpels (called a compound ovary or compound pistil) is termed syncarpous.
However, if the gynoecium consists of more than one distinct carpel, it will have more than one
pistil and is then termed apocarpous. Fertilization of the ovule or ovules results in development
of the carpel(s) into a
fruit.
The gynoecium, the collective term for all the carpels, is the innermost whorl of the parts of a
flower, and in many flowers the other parts (sepals, petals, and stamens) are attached to the
receptacle beneath the gynoecium. In such cases, where the ovary lies above the attachments of
the other distinct floral parts, the flower is described as hypogynous or as having a superior
ovary. In some species, the other (noncarpellary) floral parts are fused to form a cup called a
floral tube or hypanthium. In these flowers, the ovary lies physically lower than the lobes of the
sepals and petals and below the point of attachment of the stamen filaments — the ovary is still
considered to be superior but the flower is termed perigynous.
In those flowers in which the floral tube is fused with the ovary, the sepals, petals, and stamens
appear to grow out from the top of the ovary, and the flower is said to be epigynous and have an
inferior ovary. The position of the ovary is an important consideration in the identification and
classification of plant species, as well as the kind of fruit that develops after fertilization.
Fruits are so varied in form and development, that it is difficult to devise a classification scheme
that includes all known fruits. It will also be seen that many common terms for seeds and fruit
are incorrectly applied, a fact that complicates understanding of the terminology. Seeds are
ripened ovules; fruits are the ripened ovaries or carpels that contain the seeds.
There are three basic types of fruits:



Simple fruits can be either dry or fleshy and result from the ripening of a simple or
compound ovary with only one pistil. Dry fruits may be either dehiscent (opening to
discharge seeds), or indehiscent (not opening to discharge seeds). Fruits in which part or
all of the pericarp (fruit wall) is fleshy at maturity are simple fleshy fruits.
Aggregate fruits develop from a flower with numerous simple pistils.
Multiple fruits are formed from a cluster of flowers (called an inflorescence). Each
flower produces a fruit, but these mature into a single mass.
Seedlessness is an important feature of some fruits of commerce. Commercial cultivars of
bananas and pineapples are examples of seedless fruits. Some cultivars of citrus fruits (especially
navel oranges and mandarin oranges), table grapes, grapefruit, and watermelons are valued for
their seedlessness. In some species, seedlessness is the result of parthenocarpy, where fruits set
without fertilization. Parthenocarpic fruit set may or may not require pollination. Most seedless
citrus fruits require a pollination stimulus; bananas and pineapples do not. Seedlessness in table
grapes results from the abortion of the embryonic plant that is produced by fertilization, a
phenomenon known as stenospermocarpy which requires normal pollination and fertilization.
Placentation or ovule arrangment is another important character in the way that fruits are
classified.
1A. FRUITS FLESHY:
2A. FRUIT SIMPLE (TRUE), DERIVED FROM A FLOWER WITH 1 PISTIL
3A. 1 SEED ENCLOSED IN BONY ENDOCARP - DRUPE
3B. MORE THAN 1 SEED:
4A. NO BONY, LEATHERY OR PAPERY ENDOCARP (BERRIES):
13A. OVARY SUPERIOR:
14A. THIN SKIN - TRUE BERRIES
14B. LEATHERY SKIN WITH OILS - HESPERIDIUM
13B. OVARY INFERIOR, FRUIT WITH RIND - PEPO
4B. LEATHERY OR PAPERY ENDOCARP, INFERIOR OVARY - POME
2B. FRUIT COMPOUND (FALSE), DERIVED FROM MORE THAN 1 PISTIL:
5A. FRUIT DERIVED FROM 1 FLOWER WITH MORE THAN 1 PISTIL - AGGREGATES
5B. FRUIT DERIVED FROM MORE THAN 1 FLOWER - MULTIPLE FRUITS
1B. FRUITS DRY:
6A. INDEHISCENT:
7A. FRUITS WITH A WING - SAMARA
7B. FRUITS WITHOUT A WING:
8A. WITH A HARD SHELL - NUT
8B. WITHOUT A HARD SHELL:
9A. PERICARP FUSED ENTIRELY TO SEEDCOAT - CARYOPSIS
9B. PERICARP NOT FUSED ENTIRELY TO SEEDCOAT - ACHENE
6B. DEHISCENT:
10A. DERIVED FROM SEVERAL FUSED CARPELS, OPENING BY SLITS, PORES OR CAP CAPSULE
10B. DERIVED FROM 1 OR 2 FUSED CARPELS, DEHISCING LENGTHWISE:
11A. FRUIT WITH PERSISTENT SEPTUM (REPLUM):
15A. LONG & THIN - SILIQUE
15B. SHORT & FAT - SILICLE
11B. NO PERSISTENT SEPTUM:
12A. DEHISCENT ALONG 1 EDGE - FOLLICLE
12B. DEHISCENT ALONG 2 EDGES - LEGUME
1. Fruit fleshy………………………………………………………………………...2
1. Fruit dry……………………………………………………………………...……4
2. Fruit has multiple seeds……………………………………………….…………..3
2. Fruit has one hard seed in center………………………………………..…...........Drupe
3. Seeds are contained in cartilaginous structures in a core of the fruit.……...……..Pome
3. Seeds are not contained in structures, no core……………………….……………Berry
4. Fruit opens easily (i.e. - you can open it by hand), or has sutures (like dents) for opening
……………………………………………………...……….………..…...................6
4. Fruit does not open easily (i.e. – you need a tool to open it), no sutures…………5
5. The wall of fruit is thin and completely fused to the seed …..……….....………..Caryopsis
5. The wall is thick and not fused to the seed ………………………….……………Nut
6. Fruit has longitudinal sutures (2 dents or fissures, one along each side)…………7
6. Fruit has several sutures for splitting in many directions……………..………….Capsule
7. Outer shell is hard but thin, containing one seed …………………...……………Achene
7. Outer shell leathery, skin-like or woody, containing multiple seeds lined up in a row when
opened
……………………….............................……………………………………………Legume
I. SIMPLE FRUITS – the product of a single pistil
A. Fleshy Fruits
1) Texture homogenous, fleshy throughout
BERRY – derived from a superior ovary
FALSE BERRY – derived from an inferior ovary
2) Texture heterogeneous
a) Exterior firm, with a hard or leathery rind
HESPERIDIUM – derived from a superior ovary, distinctly segmented in cross section
PEPO – derived from an inferior ovary, not distinctly segmented
b) Exterior soft, with a hard or cartilaginous inner layer
DRUPE – derived from a superior ovary; fleshy part consisting of mesocarp, the endocarp
forming a hard central ‘pit’ or stone around the seed
POME- derived from an inferior ovary; fleshy part derived form mesocarp and also from the
hypathium, the endocarp thin and cartilaginous around the many seeds
B. Dry Fruits
1) Dehiscent, opening when ripe to release seeds
a) Developed from a simple pistil (1 carpel)
LEGUME – Dehiscing by two longitudinal sutures
FOLLICLE – dehiscing along a single longitudinal suture only
c) Developed from a compound pistil (2 or more carpels)
CAPSULE – developed from various types of superior or inferior ovaries; the following
subtypes, based on type of dehiscence, are often recognized:
SEPTICIDAL CAPSULE – sutures forming at the septa; usually more than 2 carpel
LOCULICIDAL CAPSULE – sutures forming in the locules; usually more than 2 carpels
PORICIDAL CAPSULE – dehiscing by small pores near the top; usually more than 2 carpels
CIRCUMSCISSILE CAPSULE – dehiscing by a lid
SILIQUE – elongate, narrow capsule, composed of two carpels, the pericarp falling off as two
valves, leaving the persistent septum which bears the seeds on its margins
SILICLE – similar to a silique, but short, not much longer than wide
2) Indehiscent, lacking special methods for opening; usually one or two seeded
SAMARA – fruit winged for wind dissemination
SCHIZOCARP – carpels two to many, united when immature, splitting apart at maturity
NUT – developed from a compound pistil (but only one carpel and one seed developing); the
pericarp hard and stoney
CARYOPSIS (Grain) - developed from a simple pistil, pericarp fused to the seed ACHENE –
developed from a simple-pistil, with superior ovary, pericarp not fused to the seed
CYPSELA – developed from a simple pistil with inferior ovary, pericarp not fused to the seed
II. COMPOUND FRUITS – the product of two or more pistils
AGGREGATE FRUITS – derived from several pistils of a single flower.
MULTIPLE FRUITS – derived from several to many flowers in an inflorescence
1) Fruit derived from more than one pistil
a) Fruit derived from an apocarpus gynocecium
Aggregate Fruit
b) Fruit derived from many separate flowers
Multiple fruit
2) Fruit derived from on simple pistil or from a compound pistil
a) Fruit fleshy at maturity
i) Fruit/ovary has one carpel (simple pistil); endocarp is thick
ii) Fruit/ovary has >1 carpel (compound pistil)
(1) Fruit/ovary is superior
(2) Ovary is inferior
b) Fruit dry at maturity
i) Fruit dry, one-seeded and indehiscent
(1) Fruits with wings
(2) Fruits without wings
(a) Ovary wall (pericarp) hard and bony
(b) Ovary wall (pericarp) thin
Achene
ii) Fruit dry, typically >1, seeded and dehiscent
(i) Fruit derived from a compound pistil
Capsule
(ii) Fruit derived from a simple pistil
1. Fruit dehisces along one suture
Follicle
2. Fruit dehisces along two sutures
Legume
Drupe
Berry
Pome
Samara
Nut