BOTANY 101 — FRUITS AND SEEDS

Fruits are the ripened and seed-bearing ovaries of flowers. Fruits are nearly as varied in color, form, size, texture, and number as are flowers, making them valuable tools in plant identification.

Botanists use the term “fruit” in a much broader way than does the layperson. Fruits are divided into two large categories: dry fruits and fleshy fruits.

Dry fruits – generally grey, brown, or another dull color, with a very thin and dry ovary wall, so that the food is largely confined to the seeds. These may be further subdivided based on the number of seeds and whether the fruit remains closed at maturity ( indehiscent ) or opens naturally ( dehiscent ).

• Achene – small, hard, indehiscent, one-cavitied, one-seeded fruit with a thin, almost inseparable wall, as in Helianthus annuus (sunflower).
• Samara – indehiscent, one or two-seeded winged fruit, as in Acer rubrum (red maple).
• Nuts – hard-shelled, usually one-seeded, indehiscent fruits, such as Juglans nigra (black walnut) or Carya illinoinensis (pecan).
• Grain or Caryopsis – one-seeded, indehiscent fruit of most grasses, including the cereals. The enclosed seed is almost inseparable from the enveloping ovary wall. This fruit is little more than a seed for all practical purposes.
• Capsule – dehiscent fruit composed of two or more carpels, generally with several or many seeds in each carpel, as in Gossypium spp. (cotton).
• Silique – several-seeded fruit with two carpels which pull away from the central partition at maturity, as in Iberis odorata (candytuft) and Brassica spp. (mustard).
• Silicle – a silique which is wider than long, such as in Lepidium virginicum (peppergrass).
• Legume – pod formed from a simple pistil, dehiscent along both sides, as seen in Pisum sativum (pea) and Senna alata (candle bush).
• Follicle – several-seeded fruit formed from a single carpel and splitting open along one side only. There may be two or more follicles produced by each flower, as in Mandevilla splendens (pink allamanda) and Asclepias spp. (milkweed).

Fleshy Fruits – are usually juicy and brightly colored, contrasting with their background to make them more noticeable to animals, who are responsible for their dispersal. All fleshy fruits are indehiscent and considerable fleshy tissue is developed as the ovary changes into the fruit.

• Drupe – “stone fruit”, a simple fruit produced from a single carpel, usually one-seeded, with an outer fleshy layer of tissue called the pericarp and an inner, heavy stony layer called the endocarp . Examples are Prunus persica (peach), Cocos nucifera (coconut), Mangifera indica (mango) and Olea europaea (olive).
• Berry – one or more carpels developed within a thin covering, very fleshy within, with the seeds embedded in the common flesh of a single ovary, such as Psidium guajava (guava), Lycopersicon esculentum (tomato), and Vaccinium spp. (blueberry).
• Pepo – berry-like fruit of large size, with a tough or very firm and hard outer wall (rind) which is developed from the receptacle, such as Citrullus lanatus (watermelon), Cucumis sativus (cucumber), and Cucurbita spp. (squash).

• Hesperidium – berry-like fruit of Citrus spp. (citrus) with a thick rind with numerous oil glands, and an interior fleshy part composed of wedge-shaped compartments, with or without seeds.
• Pome – fruit developed largely from the receptacle which surrounds the carpels or inedible core parts, as in Malus spp. (apple) and Pyrus pyrifolia (sand pear).
• Aggregate – fleshy fruit developed from the ovaries of a single flower, which becomes enlarged and bears many simple, true fruits resembling achenes or drupes, as in Fragaria x ananassa (strawberry). Achenes are the fruit embedded in a fleshy receptacle.
• Multiple – fruits derived from many closely clustered flowers, such as in Morus spp. (mulberry) and Ananas comosus (pineapple).

Gymnosperms – produce seeds but not true fruits since they have no ovary; such seeds are said to be naked and are borne on the inside of the scales or cones, but in plants such as Juniperus spp. (junipers) and Podocarpus spp. (podocarpus) they are embedded in a fleshy fruit-like organ, known as an aril.

Seeds – consist of an outer coat or wall, which is usually very tough, hard, or woody, within which are cotyledons and the embryo. Seeds normally have just one embryo, but sometimes have more than one, as Citrus spp. (citrus) and Mangifera indica (mango), which results in two or more new plants growing from one seed. Seeds are developed as a result of the fertilization of the egg in the ovule of the ovary of a flower. Typically seeds are oval or globular and range in size from dust-like orchid seeds to the large seed of the Persea americana (avocado), with some plants bearing seeds of even greater size such as Cocos nucifera (coconut). Seeds vary greatly in color, texture, longevity, and methods of dispersal. Some of the modifications of seeds which aid in dispersal are coverings of spines, hooks, bristles, cotton, or plumes, or having wings and arils. They also vary in the types and abundance of food they contain.

Cotyledon – these “seed leaves” are the primary leaves in the seed. In monocotyledons, the seed contains only one seed leaf and in dicotyledons it has two. In monocots, such as grasses, the single cotyledon remains inside the seed and acts as a digestive organ for the embryo. Cotyledons of dicots are often pushed up out of the seed at germination and reach above ground where they develop green color and act as true leaves. In other dicots, such as Pisum sativum (English pea), the cotyledons remain below the surface and simply provide stored food for the young plant.

Source: Botany Handbook for Florida, Revised Edition, Kathleen C. Ruppert, January 1999 — This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.