Phanerogams are said to be matured when they reach the flowering stage. The ovules of the flowers after fertilization get converted into seeds, whereas the ovary wall develops further to form the protective covering over the seed, which is known as fruit. In botany, this particular coating is also called pericarp.
Pericarp consists of three different layers, one after the other as:
1. Epicarp: The outermost coating of the pericarp and may be thin or thick.
2. Mesocarp: A layer in between epicarp and endocarp, and may be pulpy or made up of spongy parenchy- matous tissue.
3. Endocarp: The innermost layer of the pericarp, may be thin or thick or even woody.
It is not necessary that the fruits should have seeds. If the ovules do not fertilize, the seedless fruits are formed. Depending upon the number of carpels present in the flowers, and other structures, the fruits fall into (1) simple fruits, (2) aggregate fruits and (3) compound fruits.
Simple fruits
Formed from the single carpel or from syncarpous gynoe- cium. Once again depending upon the mesocarp, whether it is dry or fleshy, they are classified as dry fruits and fleshy fruits. Dry fruits are further sub-classified into dehiscent and indehiscent fruits.
Aggregate fruits
These fruits get formed from many carpels or apocarpous gynoecium, e.g. raspberry.
Compound fruits
In this particular case many more flowers come together and form the fruits, e.g. figs, pineapple.
FRUITS
Simple fruits Aggregate fruits Compound fruits
Dry fruits Fleshy fruits Dehiscents fruits
Indehiscents fruits
False fruits
Sometimes it so happens that apart from the ovary and the other floral parts like thalamus, receptacle or calyx grow and form the part of the fruit, known as false fruit or pseudo- carp. Following are the few examples of pseudocarp in
which other parts of the flower forming important part of the fruits are shown in the bracket. Strawberry (thalamus), cashew nut (peduncle and thalamus), apple (thalamus), marking nut (peduncle) and rose (thalamus)
I. Dehiscent capsular fruits:
1. Legume or pod: It is a dry monocarpellary fruit devel- oping from superior ovary, dehiscing by both the margins, i.e. senna, tamarind, pea.
2. Capsule: It is a dry one to many-chambered fruit, developing from superior or poly carpellary ovary dehisc- ing in various forms, i.e. cardamon, cotton, datura, lobelia, colchicum, digitalis, poppy.
3. Follicle: Similar to legumes and dehisces at one margin only, i.e. rauwolfia, anise, calotropis.
4. Siliqua: A dry, two-chambered fruit, developing from bicarpellary ovary, multiseeded. It dehisces from base upwards as in radish mustard, etc.
II. Indehiscest fruits:
1. Achene: A dry, one-chambered, one-seeded fruit devel- oped from superior monocarpellary ovary. Pericarp is free of seed coat, i.e. clemantis, rose.
2. Caryopsis or grain: Small, dry, one-seeded fruits, developing from simple pistil, pericarp fused with seed coat as in maize, rice, bamboo.
3. Nut: Dry, one-seeded fruits developing from superior ovary, pericarp hard and woody, i.e. areca nut, marking nut, cashew nut.
4. Samara: Dry, one- or two-seeded, winged fruit from supe- rior bi- or tricarpellary ovary, i.e. dioscorea, shorea, etc. 5. Schizocarp: These are further divided into two sub- classes.
(i) Lomentum: In this type of pod of legume is parti- tioned into one-seeded compartments as observed in acacia, ground nut, cassia fistula.
(ii) Cremocarp: Dry, two-chambered fruit, developing from an inferior bicarpellary ovary. Splitting into two, indehiscent one-seeded pieces are called mericarps, i.e. coriander, cumin, fennel, dill, etc.
Fleshy fruits:
1. Drupe (Stone fruit): A fleshy one or more seeded fruit, with pericarp well differentiated into epicarp, fleshy mesocarp and hard endocarp as in mango, olive, coconut, etc.
2. Berry: A fleshy, many-seeded fruit developed from superior, single carpel, i.e. tomato, guava, grapes, banana. 3. Pepo: Pulpy, many-seeded fruit developing from one- or three celled inferior ovary, i.e. cucumber gourd, colocynth, water melon.
4. Pome: Fleshy, one- or more-celled syncarpous fruit. Fleshy, part is thalamus, while actual fruit lies inside, e.g. apple, pear.
5. Hesperidium: A superior, many-seeded fleshy fruit endocarp forming chambers; epicarp and mesocarp fused to form skin, e.g. orange, lemon.
Drupe of mango
Pome of apple Hesperidium of orange Berry of tomato Pepo of cucumber
Fig. 4.47 Types of fl ashy fruits
Uses of fruits
1. Apart from the main source of food grains, i.e. wheat, jowar, fruits are also used for their high sugar value, minerals and vitamins.
2. Fleshy fruits like, papaya, mango, apple are used com- mercially as source of pectin.
3. Bayberry wax and olive oil are obtained industrially from fruits only.
4. Several fruits like chilies, black pepper caraway and cumin are used on large scale for the preparation of spices.
5.1. INTRODUCTION
A British systematic botanist J. Hutchinson published his work, The Families of Flowering Plants in 1926 on dicotyle- dons and in 1934 on monocotyledons. Hutchinson made it clear that the plants with sepals and petals are more primitive than the plants without petals and sepals on the assumption that free parts are more primitive than fused ones. He also believed that spiral arrangement of floral parts, numerous free stamens and hermaphrodite flowers are more primitive than unisexual flowers with fused stamens. He considered monochlamydous plants as more advanced than dicotyledons. Hutchinson’s system indicates the concept of phylogenetic classification and seems to be an advanced step over the Bentham and Hooker system of classification. Hutchinson accepted the older view of woody and herbaceous plants, and fundamentally called them as Lignosae and Herbaceae. He revised the scheme of classification in 1959. He has divided the flowering plants into two phyla: phylum I—Gymnospermae (not elaborated by him) and phylum II—Angiospermae. The latter are divided into two sub-phyla: sub-phylum I—Dicotyledons and sub-phylum II—Monocotyledons.
The division of angiosperms into these two large classes is based on the following factors:
(1) In dicotyledons, the embryo bears two cotyledons, and in monocotyledons, it bears only one.
(2) In dicotyledons, the primary root persists and gives rise to the tap root, while in monocotyledons, the primary root soon perishes and is replaced by a cluster of adventitious (fibrous) roots.
(3) As a rule, venation is reticulate in dicotyledons and parallel in monocotyledons. Among monocotyledons, aroids, sarsaparilla (Smilax) and yams (Dioscorea), however, show reticulate venation, and among dicoty- ledons, Alexandrian laurel (Calophyllum) shows parallel venation. Further, in dicotyledons, the veinlets end freely in the mesophyll of the leaf, whereas in mono- cotyledons, veins or veinlets do not end freely.
(4) The dicotyledonous flower usually has a pentamerous symmetry, sometimes tetramerous (as in Cruciferae and Rubiaceae), while the monocotyledonous flower has a trimerous symmetry.
(5) In the dicotyledonous stem, the vascular bundles are arranged in a ring and are collateral and open, i.e. they contain a strip of cambium which gives rise to secondary growth. In the monocotyledonous stem, however, the bundles are scattered in the ground tissue and are collateral and closed. Hence, there is no secondary growth (with but few exceptions). Also the bundles are more numerous in monocotyledons than in dicotyledons. Further, they are more or less oval in monocotyledons and wedge shaped in dicotyledons. (6) In the dicotyledonous root, the number of xylem
bundles varies from 2 to 6, seldom more, but in the monocotyledonous root there are many, seldom a limited number (5–8). It may also be noted that the cambium soon makes its appearance in the dicotyle- donous root as a secondary meristem and gives rise to secondary growth, but in the monocotyledonous root, the presence of cambium is rare. Hence, there is no secondary growth.