REPRODUCTION IN PLANTS 275 



wheat, and other cereal grains are fruits, and so are the pods of beans 

 and peas, nuts like walnuts and acorns, tomatoes, and many other things 

 that are not popularly considered fruits. 



According to whether the ovary was formed from one, two, or more 

 ovule-bearing structures (carpels), the fruit may contain one, two, or 

 more seed-producing areas, in one or more seed chambers. The matured 

 ovary wall may remain thin, or it may thicken greatly; it forms what is 

 called the pericarp. In many fruits the pericarp differentiates into three 

 layers — an outer skin, or exocarp; a more or less thickened middle portion, 

 or mesocarp; and an inner layer, the endocarp. In the stone fruits, such as 

 the peach, the mesocarp is fleshy, while the endocarp forms a stony wall 

 about the seed. In "nuts" like the pecan the mesocarp is a woody husk 

 surrounding a hard endocarp. In the apple the mesocarp is fleshy and the 

 endocarp thin and papery, forming the "core." Not all the flesh of the 

 apple is mesocarp, however; in this and some other fruits, such as the 

 strawberry, the receptacle enlarges and shares in formation of the fruit. 

 The most important types of fruits may be classified as follows: 1 



I. Sintple fruits, consisting of a single enlarged ovary, with which some other flower 

 parts may be incorporated. Most of the common fruits, except those listed below 

 under II and III, are simple fruits. 



A. Fleshy fruits (ovary wall fleshy, at least in part, or until maturity). 



1. Berry — the ovary wall fleshy, enclosing one or more seeds. Examples: 

 grape, gooseberry, currant, pepper, persimmon, tomato, banana, date 

 (the "stone" of the last being a seed). 



As special types of berries we have: 



a. Pepo — a type of berry with hard rind composed largely of the receptacle. 

 Examples: squash, cucumber, cantaloupe, watermelon. 



b. Hesperidium — a type of berry with leathery, oily rind, and juicy pulp 

 composed of numerous "cells." Examples: orange, grapefruit, lemon. 



2. Drupe or "stone" fruits — one-seeded, the seed enclosed in a "stone" or 

 "pit" made up of the stony endocarp; mesocarp fleshy, exocarp thin, 

 forming the skin. Examples: cherry, peach, mango, plum, olive. Such 

 "nuts" as almond, walnut and pecan also belong here; the almond is the 

 stone of a typical drupe, and the shell of walnuts and pecans is the stone 

 of a drupe, the fleshy part of which is represented by the husk. 



3. Pome — outer part of the ovary wall fleshy and enclosed in the fleshy 

 receptacle; inner part of ovary wall papery, forming the "core." Exam- 

 ples: pear, apple, quince. 



B. Dry fruits (ovary wall dry). 



1. Dehiscent fruits (splitting open when ripe). 



a. Legume or true pod — ovary composed of a single, modified, seed-bearing 

 leaf (carpel), seeds attached along one side; splitting along two sutures 

 when ripe. Examples: pea, bean, vetch. 



b. Follicle — ovary composed of one carpel; splitting along only one suture 

 when ripe. Examples: milkweed, larkspur, columbine, peony. 



1 Reprinted by permission, with modifications, from Holman and Robbins, Textbook 

 of General Botany, John Wiley & Sons, Inc., New York. 



