Lab #2: Fruit ID
Botany/Reynolds
NAME: _______________________
Introduction:
Seed plants are divided into two major categories depending on the type of seed bearing
structure. Gymnosperms (Greek for ‘naked seed’) produce cones with exposed seeds and
angiosperms (Greek for ‘covered seed) produce fruits that protect the seed. In this lab we
will focus on angiosperm fruits. The fruit (or cone) serves a variety of uses for the seed
inside, ranging from attracting animals for seed dispersal to providing aerodynamic wings to
ensure safe wind dispersal of the seed. The outer layers of the ovule also toughen to form
the seed coat, which may protect the seed from being eaten or adverse environmental
conditions, such as drought, fire, or cold.
The basic anatomy of a fruit is shown in Figures 1 and 2. There are a large variety of
types of fruit, however all fruits are essentially the mature ovaries. The 4 major categories
of fruit are: 1) fleshy (simple); 2) dry (simple); 3) aggregate; and 4) multiple. These differ
in the way they mature after fertilization of the ovules. In this lab we will look at different
types of fruits that are commonly available at the local grocery store. Pay close attention
to how they are formed and try to identify the basic parts of each fruit.
Figure 1. Characteristic Fruit Types
Simple fleshy fruits include berries, pepos,
hesperidia, drupes, and pomes. A berry is a simple
fruit with one or many seeds surrounded by a
fleshy pericarp. A large variery of fruit families
have berries as fruits. A pepo is the characteristic
fruit of the Cucumber Family (Curcurbitaceae). It
is a berry with a thick rind, like a watermelon. The
Citrus Family (Rutaceae) has a characteristic fruit
called a hesperidium. These berries have a thick
leathery rind and thin partitions between the
sections of the fruits. A drupe is a single seeded
Figure 2. Anatomy of a Simple Fruit
berry with a hard endocarp surrounding the seed.
Some “nuts” are actually the inner endocarp layers of drupes. These are called “drupaceous nuts”
and include walnuts, pecans, and coconuts (a dry drupe). Used in this sense, the pit of a plum or
peach should also be called a nut! Finally, a pome (characteristic of the Rose Family, or
Rosaceae) is a fleshy simple fruit where the edible, fleshy part is not part of the ovary, but rather
part of the floral tissue.
Dry fruits are further classified as dehiscent (splits open at maturity) and indehiscent (does
not split open). Dehiscent dry fruits include legumes, siliques, and capsules. Legumes are
characteristic of the Leguminosae group of the Bean Family (Fabaceae). These bean ‘pods’
actually represent the ‘seams’ of a folded over carpel within the pistil. The carpel contains
the ovules within the pistil and thus contains the seeds of the fertilized fruit. Inside the pod,
whether a bean or peanut, there are multiple seeds. Siliques and capsules are similar to the
pods of legumes, but they have two (siliques) or three or more (capsules) carpels. Siliques
are characteristic of the Mustard Family (Brassicaceae) and capsules are commonly found
in many plant families.
Indehiscent fruits include achenes, grains, samaras, and nuts. Achenes are single seeded
fruits, usually formed in clusters. They are characteristic of the Sunflower Family
(Asteraceae). When you eat sunflower seeds you are eating achenes, and when you blow
dandelion seeds, you are dispersing achenes! Grains (caryopsis) are characteristic of the
Grass Family (Poaceae). They are also single seeded fruits, but the seed coat is fused to the
pericarp. Just a few grains, such as wheat, oats, corn, and rice feed billions of people on
earth! Samaras are the ingenious invention of several tree families, such as Maples, Ashes,
and Elms. These one-seeded fruits (double for Maples) have characteristic wings that allow
for effective wind dispersal. Nuts are defined as one seeded fruits with a hard pericarp.
True nuts, such as acorns, beech nuts, and chestnuts sit in a scaly cup called an involucre
Multiple and aggregate fruits seem similar at first, but they differ in how they are formed.
Aggregate fruits form from multiple carpels in a single flower. Blackberries, raspberries,
and strawberries develop from a single flower in this way. In blackberries, each individual
carpel forms a small drupe, which fuse into a cluster called a syncarp. Multiple fruits, like
the pineapple, actually form from multiple flowers on a single inflorescence. As the fruits
mature, they fuse together to form a single large fruit. In the case of a pineapple, each
individual flower forms a berry and these berries join to form a pineapple.
Lab - Fruit ID & Dissection
Botany/Reynolds
Fruit Type
Drupe
Pome
Berry
Pepo
Hesperidium
Legume
Capsule
Achene
Grain (Caryopsis)
Multiple
Aggregate
Synconium
Nut
Seed (Kernel)
Fruit Name
NAME: __________________
Plant Family
Characteristics
(Scientific Name - if you
don’t know, look it up!)
(Simple/Complex? Fleshy/Dry?
Dehiscent/Indehiscent?)
Discussion Questions (research using the internet if needed!):
1) What is an accessory fruit? How is it different from other fruit types? Give an example.
2) What is parthenocarpy? Which of the fruits from today’s lab is parthenocarpic?
3) What is the botanical definition of a nut? Give an example from today’s lab of a nut
and an example of a fruit commonly misidentified as a nut.
4) Many fruits and/or seeds are commonly used as spices, such as black pepper from
today’s lab. List 3 other fruits commonly used as spices and describe them.
5) A fruits major function is to aid with seed dispersal. One fruit we didn’t look at today
is a pomegranate, a berry whose fleshy mesocarp is inedible. What is the edible part of
the fruit called? How does this assist with seed dispersal?