What is a Fruit?
Sourced from: RFC Brisbane Branch newsletter Oct Nov 2000
Most
people associate the word "Fruit" with succulent fleshy plant
structures but botanically the concept is much wider than this. All
fruits develop from a flower - the classification of which is based on
which parts of the fertilised ovary expand in size. The fruit
structures have evolved in various ways to enhance wide dispersion from
the initial plant and improve the chance of seed germination. The basic classification of fruit types is:
A. Simple Fruits formed from a single ovary which may contain more than one seed.
(i) Fleshy fruit types - berries, drupes and pomes
(ii) Dry fruit types - legumes, follicles, nuts & capsules
B. Aggregate Fruits formed from a number of ovaries in one flower fusing into a single fruit
e.g. strawberries, raspberries and blackberries.
C. Multiple Fruits formed from several flowers having the ovaries fused into a single fruit
e.g.
mulberries, pineapples and figs. Multiple Fruits can be difficult to
visualise but if the fruit development is observed on the plant,
justification for the classification can be seen.
Fleshy Fruits
Berries
have a fleshy pulp containing the seeds centrally with a thin skin
often coloured conspicuously to attract birds and animals. Typical
examples are the grape and tomato but also included is the capsicum,
carambola, mangosteen, paw-paw, passionfruit, roseapple, sapodilla,
avocado (oily flesh) and banana (seeds very rare). The citrus family
are special berries called Hesperidia the name coming from Hesper a
Greek mythological character who had a citrus grove. The skin (rind) is
inedible and the inside pulp has a high juice content but all family
members are similar - typical of lemons and oranges etc. The Cucurbit
family are also special berries called Pepos. I think Pepois Spanish
for "Gourd'' but all the family members have a hard leathery skin
including cucumbers, chokoes, pumpkins and watermelons.
Drupes
are distinguished by containing a woody pit or stone which encloses one
or occasionally two seeds. Drupe is a Greek word for "Olive" but
possibly the Apricot is a better example with its large amount of
edible flesh. Other fleshy drupes are cherries, peaches, plums mangoes
and lychees. Some drupes have almost no flesh and the inner seed is
eaten - examples being the Almond and Pecan. The coconut has an
external covering that is thick and fibrous which promotes floating in
seawater but it is nevertheless a drupe.
Pomes
of which Apples, Pears and Loquats are examples are so called from the
French word for Apple. The base of these fruits contains the residual
structure of the flower called the Calyx and the main fleshy structure
we eat is called the Hypanthium which surrounds the "core" containing
the seeds.
Dry Fruits
Legumes of which beans and peas are typical develop a pod which splits down both sides when the seeds are ripe.
Follicles
of which the Macadamia is typical, split down one side of the husk to
release the so-called "nut" botanically described as a Locule. We crack
this Locule to get at the seed typically called the Kernel.
Capsules to my knowledge do not produce edible structures but a good example is the Poppy head which resembles a salt shaker when ripe.
Nuts
are not common - the Acorn and Hazelnuts are good examples with their
special "cap" and hard leathery skin enclosing one seed. Most
commercial so-called nuts (Almond, Pecan) are Drupes.
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