Morphology of Flowering Plants

Morphology is the study of external form and structure. The previous chapters classified plants; this chapter looks at what a typical flowering plant (an angiosperm) actually looks like from the outside, organ by organ, so that you can describe any plant you are handed in the language a botanist uses. Every term in this chapter is one the examiner expects verbatim, so learn the NCERT word and the NCERT example together.

The body of a flowering plant is one axis with two ends. The part below the soil is the root system, which develops from the radicle of the embryo. The part above the soil is the shoot system, which develops from the plumule. The shoot carries the stem, the leaves at its nodes, the flowers, and after fertilisation the fruits and seeds. NCERT Figure 5.1 shows all of these on a single plant, with a leaf at each node, an axillary bud in the angle between the leaf and the stem, and a flower at the tip. A very common 1-mark item asks you to identify one of these parts or to state which embryonic structure a root or a shoot develops from.

Roots, stems and leaves are the vegetative organs; the flower, fruit and seed are the reproductive organs. Yet plants do not always keep to their basic plan. A part is sometimes changed in form and function to do a different job, and this is called a modification. Underground potato is a stem, aerial prop roots of banyan are roots, the spines of Opuntia are leaves. Telling a modified part from what it looks like at first glance is the skill the whole chapter builds, and the rule is always the same: judge an organ by its external features (nodes, internodes, buds, scale leaves, root cap, root hairs), not by where it sits.

A note on the syllabus: the rationalised NCERT print keeps the root, stem, leaf, inflorescence, flower, fruit, seed, semi-technical description and the family Solanaceae. The sub-sections on modifications of root, stem and leaf and the families Fabaceae and Liliaceae were trimmed from the print, but modifications are still asked in almost every school paper and in NEET, so this guide covers them fully and marks them as extension sections.

In most dicotyledonous plants the radicle elongates directly into the primary root, which grows into the soil and bears lateral roots of several orders (secondary, tertiary and so on). The primary root together with its branches is the tap root system, as in mustard. In monocotyledons the primary root is short-lived and is replaced by a large number of roots arising from the base of the stem; this is the fibrous root system, as in wheat. In some plants roots arise from parts of the plant other than the radicle; these are adventitious roots, as in grass, Monstera and the banyan tree. Note the exam distinction: a fibrous root system is a whole system of thin roots in monocots, whereas adventitious root is any root that does not come from the radicle, whether it forms a system or not.

The main functions of the root system are absorption of water and minerals from the soil, providing proper anchorage to the plant parts, storing reserve food material and synthesis of plant growth regulators. Give all four when asked for functions.

Regions of the root (5.1.1). From the tip upward there are four regions. (1) The root cap: a thimble-like structure covering the apex, protecting the tender tip as it pushes through the soil. (2) The region of meristematic activity, a few millimetres above the cap: its cells are very small, thin-walled and with dense protoplasm, and they divide repeatedly. (3) The region of elongation: cells proximal to the meristem undergo rapid elongation and enlargement and are responsible for the growth of the root in length. (4) The region of maturation: the cells of the elongation zone gradually differentiate and mature. From this region some epidermal cells form very fine and delicate thread-like structures called root hairs, which absorb water and minerals from the soil. Root hairs are unicellular extensions of epidermal cells; they are short-lived and are replaced as the root grows.

The examiner likes a labelled sketch of the root tip (NCERT Figure 5.3) with these four regions and root hairs marked, and a one-line function for each region.

Roots in some plants change their shape and structure and become modified to perform functions other than absorption and conduction of water and minerals. They are modified for support, storage of food and respiration. Learn each with its NCERT example; the examples are what score.

For storage. Tap roots of carrot and turnip and adventitious roots of sweet potato get swollen and store food. So carrot, turnip and radish are swollen tap roots, and sweet potato is a swollen adventitious root. This is the trap behind the classic question 'potato is a stem, sweet potato is a root': sweet potato has no nodes, no buds and no scale leaves, and it bears lateral rootlets.

For support. Hanging structures that support a banyan tree are called prop roots; they grow down from horizontal branches, enter the soil and act like pillars. The stems of maize and sugarcane have supporting roots coming out of the lower nodes of the stem; these are called stilt roots. The distinction the examiner wants: prop roots arise from the branches high up and are thick and pillar-like; stilt roots arise from the lower nodes of the stem, in a cluster, and grow obliquely into the soil.

For respiration. In some plants that grow in swampy areas, many roots come out of the ground and grow vertically upwards. Such roots are called pneumatophores, and they help to get oxygen for respiration, as in Rhizophora growing in mangrove swamps. The soil there is waterlogged and poor in oxygen, so the roots turn upward and take in air through small pores.

A 3-mark question often names three plants (say banyan, turnip, Rhizophora) and asks you to name the modification and its function. Answer in three clear lines: plant, name of modification, function.

The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits. It develops from the plumule of the embryo of a germinating seed. The stem bears nodes and internodes: the region of the stem where leaves are born is the node, and the portion between two nodes is the internode. The stem bears buds, which may be terminal (at the tip) or axillary (in the angle between leaf and stem). The stem is generally green when young and later often becomes woody and dark brown.

The main function of the stem is spreading out branches bearing leaves, flowers and fruits. It conducts water, minerals and photosynthates. Some stems perform the function of storage of food, support, protection and vegetative propagation. That list of functions is the full 2-mark answer.

What makes a stem a stem is the presence of nodes and internodes, buds (terminal and axillary) and leaves or scale leaves. This is the test you apply to any doubtful underground part. Potato has nodes with 'eyes' (each eye is a group of axillary buds in the axil of a scale leaf), ginger has nodes, internodes and scaly leaves, onion bulb has a short conical stem carrying fleshy leaves and a terminal bud. None of them has a root cap or root hairs. So all three are stems. Hence the NCERT exercise statement 'underground parts of a plant are not always roots'.

Herbaceous stems are soft and green, woody stems are hard and brown. Stems may be erect, or weak and creeping (trailing) or climbing with the help of tendrils or hooks. Remember these plain descriptors; they are the words you will use in the vegetative part of a semi-technical description: stem herbaceous or woody, aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous.

The stem may not always be typically like what it is expected to be. It is modified to perform different functions. Group the modifications by function, as NCERT does, and attach an example to each.

Underground stems for storage and perennation. Underground stems of potato, ginger, turmeric, zaminkand and Colocasia are modified to store food in them. They also act as organs of perennation to tide over conditions unfavourable for growth. Potato is a tuber (a swollen tip of an underground branch with eyes), ginger and turmeric are rhizomes (horizontal, with nodes, internodes and scaly leaves), zaminkand and Colocasia are corms (short, vertical, swollen, with a terminal bud).

Tendrils for climbing. Stem tendrils which develop from axillary buds are slender and spirally coiled and help plants to climb, as in gourds (cucumber, pumpkins, watermelon) and grapevines.

Thorns for protection. Axillary buds of stems may also get modified into woody, straight and pointed thorns, as in Citrus and Bougainvillea. They protect plants from browsing animals.

Photosynthesis in arid regions. Some plants of arid regions modify their stems into flattened (Opuntia) or fleshy cylindrical (Euphorbia) structures. They contain chlorophyll and carry out photosynthesis; such a stem is called a phylloclade.

Vegetative propagation. Underground stems of some plants such as grass and strawberry spread to new niches and, when older parts die, new plants are formed (runner). In plants like mint and jasmine a slender lateral branch arises from the base of the main axis and, after growing aerially for some time, arches downwards to touch the ground (stolon). A lateral branch with short internodes and each node bearing a rosette of leaves and a tuft of roots is found in aquatic plants like Pistia and Eichhornia (offset). In banana, pineapple and Chrysanthemum the lateral branches originate from the basal and underground portion of the main stem, grow horizontally beneath the soil and then come out obliquely upward, giving rise to leafy shoots (sucker).

Also know the pair that is asked in 'differentiate' questions: a phylloclade is a green flattened or fleshy stem (Opuntia), whereas a phyllode is a green flattened petiole doing the work of the leaf (Australian Acacia).

The leaf is a lateral, generally flattened structure borne on the stem. It develops at the node and bears a bud in its axil. The axillary bud later develops into a branch. Leaves originate from shoot apical meristems and are arranged in an acropetal order (oldest at the base, youngest at the tip). They are the most important vegetative organs for photosynthesis.

A typical leaf has three main parts: leaf base, petiole and lamina. The leaf is attached to the stem by the leaf base and may bear two lateral small leaf-like structures called stipules. In monocotyledons the leaf base expands into a sheath covering the stem partially or wholly. In some leguminous plants the leaf base may become swollen, which is called the pulvinus. The petiole helps hold the blade to light; long thin flexible petioles allow leaf blades to flutter in wind, thereby cooling the leaf and bringing fresh air to the leaf surface. The lamina or leaf blade is the green expanded part with veins and veinlets. There is usually a middle prominent vein, the midrib. Veins provide rigidity to the leaf blade and act as channels of transport for water, minerals and food materials.

5.3.1 Venation. The arrangement of veins and veinlets in the lamina of a leaf is termed venation. When the veinlets form a network, the venation is reticulate (dicotyledons). When the veins run parallel to each other within a lamina, the venation is parallel (monocotyledons). This is a favourite 2-mark question and a favourite MCQ.

5.3.2 Types of leaves. A leaf is simple when its lamina is entire or when incised, the incisions do not touch the midrib. When the incisions of the lamina reach up to the midrib breaking it into a number of leaflets, the leaf is called compound. A bud is present in the axil of the petiole in both simple and compound leaves, but not in the axil of leaflets of the compound leaf; this is how you tell a leaflet from a leaf. Compound leaves are of two types. In a pinnately compound leaf a number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf, as in neem. In a palmately compound leaf the leaflets are attached at a common point, at the tip of the petiole, as in silk cotton (Bombax).

5.3.3 Phyllotaxy. Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. It is of three types. In alternate phyllotaxy a single leaf arises at each node in alternate manner, as in china rose, mustard and sunflower. In opposite phyllotaxy a pair of leaves arises at each node and lies opposite to each other, as in Calotropis and guava. If more than two leaves arise at a node and form a whorl, it is whorled, as in Alstonia.

Leaves are often modified to perform functions other than photosynthesis. Five modifications appear in NCERT, each with one example, and a 3-mark question ('How do various leaf modifications help plants?') expects all five.

Tendrils. Leaves are converted into tendrils for climbing, as in peas. In pea the terminal leaflets of the pinnately compound leaf become thread-like, coiling tendrils that hold the plant up on a support. Contrast with the stem tendrils of cucumber and grapevine.

Spines. Leaves are converted into spines for defence, as in cacti. Reducing the leaf to a spine also cuts water loss in a desert plant; photosynthesis is taken over by the green flattened stem, the phylloclade (Opuntia).

Fleshy leaves for storage. The fleshy leaves of onion and garlic store food. The onion bulb is a short conical stem carrying these fleshy leaves; the outer dry scales are also leaves.

Phyllode. In some plants such as Australian Acacia the leaves are small and short-lived. The petioles in these plants expand, become green and synthesise food. This flattened green petiole is a phyllode. (Phyllode = petiole; phylloclade = stem.)

Insect-catching leaves. Leaves of certain insectivorous plants such as pitcher plant (Nepenthes) and venus fly trap (Dionaea) are modified to trap insects. In the pitcher plant the lamina forms the pitcher, the apex of the leaf the lid, and the petiole a tendril-like stalk; the plant grows in nitrogen-poor soil and digests the insect for nitrogen.

When answering, always pair the modification with its function and its example: 'Leaf tendril, for climbing, pea.' Three words score; a paragraph without the example does not.

A flower is a modified shoot. The shoot apical meristem changes to a floral meristem. Internodes do not elongate, so the axis gets condensed. The apex produces different kinds of floral appendages laterally at successive nodes instead of leaves. When a shoot tip transforms into a flower, it is always solitary. This four-line argument is the complete answer to the NCERT exercise 'Justify: flower is a modified shoot', and the examiner ticks each line.

The arrangement of flowers on the floral axis is termed the inflorescence. Depending on whether the apex gets converted into a flower or continues to grow, two major types are defined.

Racemose inflorescence. The main axis continues to grow (it has unlimited growth), and the flowers are borne laterally in an acropetal succession: the oldest flowers are at the base and the youngest near the tip. The main axis never ends in a flower. Examples usually quoted: mustard, radish, Fabaceae plants.

Cymose inflorescence. The main axis terminates in a flower, hence it is of limited growth. The flowers are borne in a basipetal order: the terminal flower is the oldest and the younger flowers arise below it on lateral branches. Examples: Solanum (as NCERT notes under Solanaceae), jasmine, Calotropis.

Two differences are enough for a 2-mark question: (i) growth of main axis, unlimited versus limited; (ii) order of flowers, acropetal versus basipetal. A third if asked: the main axis does not end in a flower versus ends in a flower.

Note the phrase 'basis for the different types of inflorescence' in NCERT exercise 13: the basis is whether the apex is converted into a flower or continues to grow. Say that first, then describe the two types.

The flower is the reproductive unit in the angiosperms. It is meant for sexual reproduction. A typical flower has four different kinds of whorls arranged successively on the swollen end of the stalk or pedicel, called the thalamus or receptacle. These are calyx, corolla, androecium and gynoecium. Calyx and corolla are accessory organs, while androecium and gynoecium are reproductive organs. In some flowers like lily the calyx and corolla are not distinct and are termed perianth. When a flower has both androecium and gynoecium it is bisexual; a flower having either only stamens or only carpels is unisexual.

Symmetry. In symmetry, the flower may be actinomorphic or zygomorphic. When a flower can be divided into two equal radial halves in any radial plane passing through the centre, it is actinomorphic (radial symmetry), as in mustard, datura, chilli. When it can be divided into two similar halves only in one particular vertical plane, it is zygomorphic (bilateral symmetry), as in pea, gulmohur, bean, Cassia. A flower is asymmetric (irregular) if it cannot be divided into two similar halves by any vertical plane passing through the centre, as in canna.

Merosity. A flower may be trimerous, tetramerous or pentamerous when the floral appendages are in multiples of 3, 4 or 5 respectively. Monocots are typically trimerous (lily), mustard is tetramerous, Solanaceae and Fabaceae are pentamerous.

Bracts. Flowers with bracts, reduced leaves found at the base of the pedicel, are called bracteate, and those without bracts ebracteate.

Position of the ovary on the thalamus. Based on the position of calyx, corolla and androecium in respect of the ovary, flowers are of three kinds. In hypogynous flowers the gynoecium occupies the highest position while the other parts are situated below it; the ovary is said to be superior, as in mustard, china rose and brinjal. In perigynous flowers the gynoecium is situated in the centre and the other parts of the flower are located on the rim of the thalamus almost at the same level; the ovary is said to be half inferior, as in plum, rose, peach. In epigynous flowers the margin of the thalamus grows upward enclosing the ovary completely and getting fused with it, and the other parts of the flower arise above the ovary; the ovary is said to be inferior, as in guava, cucumber and the ray florets of sunflower. NCERT exercise 15 asks exactly this, and a 3-mark answer needs the three definitions, the three ovary positions and the examples, with three small sketches (NCERT figure).

Each flower normally has four floral whorls: calyx, corolla, androecium and gynoecium, from outside inward. Learn the terms for each whorl exactly.

Calyx. The calyx is the outermost whorl and its members are called sepals. Generally sepals are green, leaf-like and protect the flower in the bud stage. The calyx may be gamosepalous (sepals united) or polysepalous (sepals free). In Solanaceae the calyx is gamosepalous and also persistent, remaining attached to the fruit (look at the green cap on a brinjal or tomato).

Corolla. The corolla is composed of petals. Petals are usually brightly coloured to attract insects for pollination. Like the calyx, the corolla may be gamopetalous (petals united) or polypetalous (petals free). The shape and colour of the corolla vary greatly; it may be tubular, bell-shaped, funnel-shaped or wheel-shaped.

Aestivation. The mode of arrangement of sepals or petals in a floral bud with respect to the other members of the same whorl is known as aestivation. The main types are valvate, twisted, imbricate and vexillary. When sepals or petals in a whorl just touch one another at the margin without overlapping, it is valvate, as in Calotropis. If one margin of the appendage overlaps that of the next one and so on, it is twisted, as in china rose, lady's finger and cotton. If the margins of sepals or petals overlap one another but not in any particular direction, it is imbricate, as in Cassia and gulmohur. In pea and bean flowers there are five petals, the largest (standard) overlaps the two lateral petals (wings), which in turn overlap the two smallest anterior petals (keel); this is vexillary or papilionaceous aestivation, as in pea and bean.

The 3-mark version of this question gives the four names and asks for the definition, an example and a small top-view sketch of each (the NCERT figure: five petals drawn as a ring, edges touching in valvate, each overlapping the next in one direction in twisted, overlapping without pattern in imbricate, and the standard-wings-keel arrangement in vexillary). Draw the sketches; they are the difference between 2 and 3 marks.

Androecium. The androecium is composed of stamens. Each stamen, which represents the male reproductive organ, consists of a stalk or filament and an anther. Each anther is usually bilobed, and each lobe has two chambers, the pollen sacs. Pollen grains are produced in pollen sacs. A sterile stamen is called a staminode. Stamens of a flower may be united with other members such as petals or among themselves. When stamens are attached to the petals they are epipetalous, as in brinjal; when attached to the perianth they are epiphyllous, as in lily. The stamens in a flower may either remain free (polyandrous) or may be united in varying degrees: in one bunch or one bundle, monadelphous (china rose); in two bundles, diadelphous (pea); in more than two bundles, polyadelphous (citrus). There may be variation in the length of filaments within a flower, as in Salvia and mustard.

Gynoecium. The gynoecium is the female reproductive part of the flower and is made up of one or more carpels. A carpel consists of three parts, the stigma, style and ovary. The ovary is the enlarged basal part, on which lies the elongated tube, the style. The style connects the ovary to the stigma. The stigma is usually at the tip of the style and is the receptive surface for pollen grains. Each ovary bears one or more ovules attached to a flattened cushion-like placenta. When more than one carpel is present, they may be free, as in lotus and rose, and are called apocarpous; they are termed syncarpous when carpels are fused, as in mustard and tomato. After fertilisation the ovules develop into seeds and the ovary matures into a fruit.

Placentation. The arrangement of ovules within the ovary is known as placentation. It is of five types. Marginal: the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, as in pea. Axile: the placenta is axial and the ovules are attached to it in a multilocular ovary, as in china rose, tomato and lemon. Parietal: the ovules develop on the inner wall of the ovary or on the peripheral part; the ovary is one-chambered but becomes two-chambered due to the formation of a false septum, as in mustard and Argemone. Free central: the ovules are borne on the central axis and septa are absent, as in Dianthus and Primrose. Basal: the placenta develops at the base of the ovary and a single ovule is attached to it, as in sunflower and marigold.

The 5-mark placentation question needs the definition, the five types each with a one-line description and example, and five transverse-section sketches (NCERT figure). Draw a circle for the ovary wall and place the ovules where the placenta is: at the suture (marginal), on the central axis with septa (axile), on the wall (parietal), on a central column without septa (free central), one ovule at the bottom in a longitudinal view (basal).

The fruit is a characteristic feature of the flowering plants. It is a mature or ripened ovary, developed after fertilisation. If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic fruit; such fruits are seedless, as in banana and some grapes.

Generally the fruit consists of a wall or pericarp and seeds. The pericarp may be dry or fleshy. When the pericarp is thick and fleshy it is differentiated into three layers: the outer epicarp, the middle mesocarp and the inner endocarp.

NCERT uses two fruits to show this. In mango and coconut the fruit is known as a drupe. They develop from monocarpellary superior ovaries and are one-seeded. In mango the pericarp is well differentiated into an outer thin epicarp (the skin), a middle fleshy edible mesocarp (the pulp) and an inner stony hard endocarp (the 'stone' around the seed). In coconut the mesocarp is fibrous (the coir), the endocarp is the hard shell and the edible part is the endosperm of the seed, not the pericarp. 'Which part of mango is edible?' is a routine 1-mark question; the answer is mesocarp.

Two more terms are asked in school papers though they sit outside the NCERT text. A true fruit develops from the ovary alone (mango, tomato). A false fruit (pseudocarp) develops from the ovary together with other floral parts such as the thalamus, as in apple and cashew, where the fleshy edible part is the thalamus. Keep the answer to that level; the examiner wants the source of the fleshy part, not a classification of fruit types.

The ovules after fertilisation develop into seeds. A seed is made up of a seed coat and an embryo. The embryo is made up of a radicle, an embryonal axis and one (as in wheat, maize) or two cotyledons (as in gram and pea).

5.7.1 Structure of a dicotyledonous seed (gram, bean). The outermost covering is the seed coat, which has two layers, the outer testa and the inner tegmen. The hilum is a scar on the seed coat through which the developing seed was attached to the fruit. Above the hilum is a small pore, the micropyle, through which water enters at germination. Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons. The cotyledons are often fleshy and full of reserve food materials. At the two ends of the embryonal axis are present the radicle and the plumule. In some seeds such as castor the endosperm, formed as a result of double fertilisation, is a food-storing tissue; such seeds are endospermic. In plants such as bean, gram and pea the endosperm is not present in mature seeds because it is consumed by the developing embryo; they are non-endospermic.

5.7.2 Structure of a monocotyledonous seed (maize). Generally monocotyledonous seeds are endospermic, but some, as in orchids, are non-endospermic. In the cereals such as maize the seed coat is membranous and generally fused with the fruit wall (which is why a maize grain is technically a fruit, a caryopsis). The endosperm is bulky and stores food. The outer covering of the endosperm separates the embryo by a proteinous layer called the aleurone layer. The embryo is small and situated in a groove at one end of the endosperm. It consists of one large and shield-shaped cotyledon known as the scutellum and a short axis with a plumule and a radicle. The plumule and radicle are enclosed in sheaths called the coleoptile and coleorhiza respectively.

NCERT exercise 7 asks for labelled diagrams of a gram seed and a vertical section of a maize grain, and this is the most reliable diagram question of the chapter. The maize V.S. must show: seed coat fused with the fruit wall, endosperm, aleurone layer, scutellum, coleoptile, plumule, radicle, coleorhiza. The gram seed must show: testa, tegmen (as seed coat), hilum, micropyle, cotyledons, plumule, radicle. Practise both until each takes under two minutes.

Various morphological features are used to describe a flowering plant. The description has to be brief, in simple and scientific language, and in a proper sequence. The plant is described beginning with its habit, then the vegetative characters (roots, stem and leaves) and then the floral characters (inflorescence and flower parts: calyx, corolla, androecium, gynoecium, fruit, seed). After describing the various parts, a floral diagram and a floral formula are presented. This sequence is itself a 2-mark answer ('what is a semi-technical description?').

Floral formula. The floral formula is represented by symbols. Br stands for bracteate, K for calyx, C for corolla, P for perianth, A for androecium, G for gynoecium, G with a line below it (written here as G̲) for a superior ovary and G with a line above it for an inferior ovary, ♂ for male, ♀ for female, ⚥ for bisexual, ⊕ for actinomorphic and % for zygomorphic. Fusion (cohesion, union of members of the same whorl) is indicated by enclosing the figure within a bracket, so K(5) means five united sepals and C5 means five free petals. Adhesion (union between different whorls, as epipetalous stamens) is shown by a line drawn above the symbols of the floral parts concerned, for example an arc joining C and A. A '+' inside a whorl shows members in two series, as A3+3 or A(9)+1.

Worked example (NCERT exercise 14): an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carpels with superior ovary and axile placentation is written ⊕ ⚥ K(5) C5 A5 G̲(2). Read it back: ⊕ actinomorphic, ⚥ bisexual, K(5) gamosepalous, C5 polypetalous, A5 five free stamens, G̲(2) two fused carpels with superior ovary (hypogynous). Axile placentation is not shown in the formula; it appears in the floral diagram.

Floral diagram. A floral diagram provides information about the number of parts of a flower, their arrangement and the relation they have with one another. The position of the mother axis with respect to the flower is represented by a dot on the top of the floral diagram. Calyx, corolla, androecium and gynoecium are drawn in successive whorls, calyx being the outermost and gynoecium in the centre. The floral diagram also shows cohesion and adhesion within parts of whorls and between whorls, and the transverse section of the ovary in the centre shows the number of locules and the placentation.

In an exam, the pair 'floral formula + floral diagram' is asked for Solanaceae almost every year. Write the formula in one line, draw the diagram with the dot on top, five sepals (united), five petals (united, valvate), five stamens attached to the petals, and a bilocular ovary with swollen axile placenta in the centre.

Solanaceae, the potato family (Solanum nigrum, potato, tomato, brinjal, chilli, petunia, tobacco). This is the one family retained in the rationalised NCERT print and it is asked for 3 or 5 marks with the floral formula and floral diagram.

Vegetative characters. Plants mostly herbs, shrubs, rarely small trees. Stem: herbaceous, rarely woody, aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous, underground stem in potato (tuber). Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation reticulate.

Floral characters. Inflorescence: solitary, axillary or cymose as in Solanum. Flower: bisexual, actinomorphic. Calyx: sepals five, united (gamosepalous), persistent, valvate aestivation. Corolla: petals five, united (gamopetalous); valvate aestivation. Androecium: stamens five, epipetalous. Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta swollen with many ovules, axile placentation. Fruit: berry (tomato, brinjal) or capsule (datura). Seeds: many, endospermous. Floral formula: ⊕ ⚥ K(5) C(5) A5 G̲(2), with a line of adhesion above C and A to show the epipetalous stamens.

Economic importance. Many plants of this family are a source of food (tomato, brinjal, potato), spice (chilli), medicine (belladonna, ashwagandha), fumigatory (tobacco) and ornamentals (petunia).

Fabaceae (extension). The pea family, earlier called Papilionoideae, a subfamily of Leguminosae. Trees, shrubs, herbs; root with root nodules. Stem erect or climber. Leaves alternate, pinnately compound or simple; leaf base pulvinate; stipulate; reticulate venation. Inflorescence racemose. Flower bisexual, zygomorphic. Calyx: sepals five, gamosepalous; valvate or imbricate aestivation. Corolla: petals five, polypetalous, papilionaceous (a posterior standard, two lateral wings, two anterior ones forming a keel which encloses the stamens and pistil), vexillary aestivation. Androecium: ten stamens, diadelphous (9)+1, anthers dithecous. Gynoecium: ovary superior, monocarpellary, unilocular with many ovules, style single, marginal placentation. Fruit legume; seeds one to many, non-endospermic. Floral formula: % ⚥ K(5) C1+2+(2) A(9)+1 G̲1. Economic importance: pulses (gram, arhar, sem, moong, soyabean), edible oil (soyabean, groundnut), dye (Indigofera), fibres (sunhemp), fodder (Sesbania, Trifolium), ornamentals (lupin, sweet pea), medicine (muliathi).

Liliaceae (extension). The lily family, a characteristic representative of monocotyledonous plants. Perennial herbs with underground bulbs, corms or rhizomes. Leaves mostly basal, alternate, linear, exstipulate with parallel venation. Inflorescence solitary or cymose, often umbellate clusters. Flower bisexual, actinomorphic. Perianth: tepals six (3+3), often united into a tube; valvate aestivation. Androecium: stamens six, (3+3), epiphyllous. Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with many ovules, axile placentation. Fruit capsule, rarely berry; seed endospermous. Floral formula: Br ⊕ ⚥ P(3+3) A3+3 G̲(3). Economic importance: ornamentals (tulip, Gloriosa), medicine (Aloe), vegetables (Asparagus), and the source of colchicine (Colchicum autumnale).