In this article we will discuss about:- 1. Characters of Mimosaceae 2. Distribution of Mimosaceae 3. Economic Importance 4. Important Types.
Characters of Mimosaceae:
Trees or shrubs; leaves bipinnate and stipulate, stipule may be modified into spines; inflorescence cymose head or head; flowers actinomorphic, hermaphrodite, small, tetra or pentamerous; calyx and corolla valvate; petals connate below, stamens number varies from 4 (Mimosa) to many (Acacia, Albizzia); carpel one; fruit legume.
A. Vegetative characters:
Habit:
Herbs (Mimosa), climbers (Entada) and trees (Acacia, Albizzia) and hydrophytic (Neptunia oleracea). Many members are xerophytic (Acacia, Prosopis).
Root:
Tap, much branched and deep.
Stem:
Erect or climbing woody, branched angular or cylindrical, solid, covered with bark, some species yield gum, sometimes spiny.
Leaf:
Cauline, ramal, alternate, pinnate or bipinnate compound, stipulate, stipules may be modified into spines, petiolate; in some species of Acacia the petiole becomes flattened into a phyllode and leaflets fall down; leaflets show movements (Mimosa, Neptunia).
B. Floral characters:
Inflorescence:
Cymose head (Acacia), spike or racemose (Dichrostachys and Prosopis).
Flower:
Pedicellate or sub-sessile (Acacia) or sessile (Prosopis), bracteate, actinomorphic, hermaphrodite, hypogynous, complete, tetra or pentamerous, small.
Calyx:
Sepals 5, gamosepalous, valvate or imbricate (Parkia), green or petaloid (Acacia nilotica), inferior.
Corolla:
Petals 5, polypetalous or gamopetalous (Acacia, Albizzia) valvate, inferior.
Androecium:
4 free in Mimosa, 10 free in Prosopis, indefinite and monadelphous in Albizzia, filaments long, anthers dithecous, pollen grains often in packets; often gland dotted to attract the insects.
Gynoecium:
Monocarpellary, ovary superior, unilocular, marginal placentation, one or many ovules in a carpel; style long and filiform; stigma minute and simple.
Fruit:
A legume or lomentum.
Seed:
Non-endospermic.
Floral formula:
Distribution of Mimosaceae:
It is commonly called Acacia family. It includes 40 genera and 2000 species. The members are mostly distributed in tropical and sub-tropical regions. In India it is represented by 12 genera and 90 species.
Economic Importance of Mimosaceae:
The sub-family is not of much economic importance. A few members are however useful.
1. Acacia catechu serves as a host for the lac insects. From this plant Katha is also obtained. Gum arabic is obtained from the barks of A. nilotica (syn. A. arabica) and A. Senegal. Saresh- a type of gum – is obtained from Albizzia lebbek.
The flowers of A. decurrens var. dealbata yield a perfume.
The bark of Acacia yields tannin which is used in leather tanning.
2. The wood of Adenanthera pavonina is powdered and yields a red dye.
3. Prosopis spicigera is grown as a hedge plant and also as a wind breaker in Rajasthan to check spreading desert, acts as water indicator.
4. Durable timber is obtained from Acacia melanoxylon, Lysistoma sabicu, Xylia dolabriformis (Iron wood).
Primitive characters:
1. Plants are mostly trees shrubs.
2. Leaves are stipulate and spirally arranged.
3. Flowers actinomorphic, hermaphrodite and hypogynous.
4. Petals are mostly free.
5. Stamens are numerous and free.
Advanced characters:
1. Leaves are compound and in many stipules are modified into spines.
2. Leaves modified into phyllode in Australian Acacias.
3. Flowers are small and inconspicuous.
4. Calyx is gamosepalous.
5. Reduction in number of petals and stamens (Mimosa).
6. Gynoecium is monocarpellary and unilocular.
7. Fruit is simple-pod.
8. Seeds are non-endospermic.
Common plants of the sub-family:
1. Acacia:
Tree or shrub, with yellow flowers in rounded head.
2. Albizzia lebbek (Siris):
Silk flower, flowers in round heads, flower fragrant.
3. Mimosa – H. Chuimui:
Leaves are highly sensitive, showing sleep movements.
4. Neptunia oleracea:
An aquatic, common water weed.
5. Parkia roxburghii:
A handsome avenue tree.
6. Prosopis:
Prickly tree or shrub. Prosopis spicigera- tree of arid regions; it is water indicator.
7. Entada:
A woody climber.
8. Xylia:
Iron wood tree.
Important Types of Mimosaceae:
1. Acacia nilotica (Linn.) Dd. (Syn. A. arabica Wild) (Fig. 54.1):
Habit:
Tree.
Root:
Tap, branched, deep.
Stem:
Erect, cylindrical, solid, woody, branched.
Leaf:
Compound, bipinnate, alternate, petiolate, stipulate, modified into spines, leaflet oblong with entire margin, obtuse, or retuse, opposite, unicostate reticulate venation.
Inflorescence:
Cymose head.
Flower:
Small, sessile, bracteate (bracts caducous), brocteolate, actinomorphic, complete, hermaphrodite, pentamerous, hypogynous.
Calyx:
Sepals 5, gamosepalous, campanulate, valvate aestivation, inferior.
Corolla:
Petals 5, yellow, gamopetalous, tubular, valvate aestivation, inferior.
Androecium:
Stamens numerous, polyandrous, filament long, anthers small, versatile, introrse.
Gynoecium:
Monocarpellary, ovary superior, unilocular, marginal placentation, style long filiform and stigma minute.
Floral formula:
2. Mimosa pudica (Fig. 54.2):
Habit:
Herb, widely spreading and diffuse; cultivated in gardens as an ornamental plant.
Root:
A nodulated, much branched tap root.
Stem:
Erect, herbaceous above and woody below, solid, branched, prickly.
Leaf:
Compound-bipinnate with distinct pulvinus, sensitive to contact, stipulate, stipules modified into spines, petiolate, petiole long and prickly, alternate.
Leaflet:
10-20 pairs, sessile, opposite, oblong, entire, acute, unicostate reticulate venation.
Inflorescence:
A globose, cymose axillary head, pink.
Flower:
Bracteate, sub-sessile, complete, hermaphrodite, actinomorphic, tetramerous, hypogynous, pink.
Calyx:
Sepals 4, gamosepalous, campanulate, valvate, inferior.
Corolla:
Petals 4, polypetalous, filaments long, anthers dithecous, introrse, dorsifixed or versatile, inferior.
Gynoecium:
Monocarpellary, superior, unilocular, marginal placentation, many ovules; style long and filiform; stigma terminal, minute.
Fruit:
A pod or lomentum, 3-6 jointed, covered with bristles.
Seed:
Non-endospermic.
Floral formula:
3. Albizzia lebbek, Siril:
Habit:
A large tree, cultivated along the roadside.
Root:
Much deep, branched tap root system.
Stem:
Erect, branched, woody, young branched pubescent, solid.
Leaf:
Compound, bipinnate, petiolate, petiole long-with a gland at the base, stipule-minute caducous.
Leaflets:
3-9 pairs of leaflets, opposite, sessile or sub-sessile, oblique, oblong, entire, upper surface green or mottled with white, under surface lighter, unicostate reticulate venation.
Inflorescence:
Flowers in cymose heads, central flower of a head is largest and old; the heads are arranged in axillary clusters.
Flower:
Bracteate, pedicellate, complete, actinomorphic, hermaphrodite, hypogynous, regular, small, fragrant, bracts linear, tomentose, caducous.
Calyx:
Sepals 5, gamosepalous, campanulate, 5-toothed, pubescent, greenish white, inferior.
Corolla:
Petals 5, gamopetalous, 5-lobed, tubular, white, inferior, pubescent, corolla tube twice longer than calyx.
Androecium:
Stamens many, united at the base, monadelphous; filaments longer than corolla tube, anthers dithecous, small, introrse.
Gynoecium:
Monocarpellary, superior, unilocular, marginal placentation, ovules many on the ventral suture; style filiform, stigma capitate.
Fruit:
A leguminous pod, flattened, 7-30 cms. long, straight.
Seed:
Non-endospermic, pale yellow.
Floral formula:
Division of the family Fabaceae and chief genera:
The main family Leguminosae is sometimes made as a separate order, with the 3 divisions as families. But generally the family is divided into 3 sub-families.
Sub-family I. Papilionaceae:
This sub-family is divided on the basis of stamen character into.
Stamens free or almost so:
1. Sophoreae:
Leaves pinnate or unifoliate, a joint between petiole and lamina, Myroxylon, Baphia, Sophora.
2. Podalyrieae:
Leaves simple with no joint between petiole and lamina, tri or polyfoliate. Anagyris, Podalyria.
Stamens mon- or di-adelphous:
(A) herbs or shrubs, pods dehiscent unless short and 1-2 seeded or inflated:
(a) Pods never transversely jointed,
(i) Leaves never stipulate:
3. Genisteae:
Usually shrubs leaves, simple or tri- or polyfoliate, leaflets entire, stamens monadelphous, anthers often of 2 sizes. Crotalaria, Lupinus etc.
4. Trifolieae:
Herbs, leaves trifoliate, pinnate, leaflets toothed, corolla glabrous; stamens mon- or – diadelphous; Medicago, Melilotus trifolium etc.
5. Loteae:
Leaves pinnately 3-many foliate, leaflets entire; corolla glabrous; stamens mon- or di-adelphous, filaments usually dilated at the tip. Lotus, Anthyllis.
6. Galegeae:
Leaves pinnately 5-indefinite or rarely 3 or 1-foliate, rachis never ending in a tendril; stamens usually diadelphous. Indigofera, Tephrosia, Sesbania, Astragalus etc.
7. Fabeae:
Leaves paripinnate, without stipules, rachis ending in a point or tendril; stamens 10, diadelphous. Cicer, Vicia, Lens, Pisum etc.
8. Abreae:
Shrubs or twiners woody at the base; leaves paripinnate, rachis ending in a point, usually stipulate, stamens 9, united. Abrus.
9. Phaseoleae:
Often twining; leaves pinnately 3-foliate, usually stipulate, leaflets entire or lobed; stamens di- or sub-monadelphous. Glycine, Rhynchosia, Phaseolus, Vigna, Dolichos etc.
10. Hedysareae:
Leaves stipulate or not. Hedysarum, Arachis, Desmodium etc.
(B) Trees, shrubs or lianes; pods indehiscent.
11. Dalbergieae:
Leaves pinnately 5-indefinite foliate, rarely 3-1 foliate, stipulate or not. Dalbergia, Derris, etc.
Sub-family II. Caesalpiniodeae:
A. Leaves bipinnate:
1. Dimorphandreae:
Flowers small, in spikes or spike-like racemes. Calyx lobes connate below into a short tube extending beyond the hypanthium. Dimorphandra.
2. Caesalpinieae:
Flowers usually medium to large, in racemes or panicles of racemes. Sepals 5, free. Caesalpinia.
B. Leaves simply pinnate or sometimes simple or unifoliate:
3. Cassieae:
Sepals distinct in bud, free to base; anthers firm in texture, dehiscing by pores, sometimes by slits as long as anther, which is then basifixed; leaves normally simply pinnate. Cassia.
4. Sclerolobieae:
Leaves imparipinnate, anthers dorsifixed, dehiscence by slits.
5. Cynometreae:
Leaves paripinnate or simple; bracteoles small or large, not enclosing the flower-buds, enclosing them, but then never valvate. Cynometrea.
6. Amherstieae:
Leaves paripinnate or simple, bracteoles well developed, enclosing the flower-buds, valvate, usually persistent. Amherstia.
7. Bauhinieae (Cercideae):
Leaves usually simple or bilobed, entire, calyx shortly toothed or lobed in bud. Stamens 10 or fewer. Bauhinia.
8. Swartizieae:
Leaves simply pinnate, rarely unifoliate; calyx entire in bud, closed, not divided into sepals, becoming variously lobed or slit as flower opens.
Sub-family III. Mimosoideae:
This sub-family is divided into 6 tribes on the basis of calyx and stamens:
A. Calyx valvate:
(a) Stamens more than 10:
1. Ingeae:
Stamens united into a tube. Inga, Albizzia.
2. Acacieae:
Stamens free or only slightly joined at base, Acacia.
(b) Stamens as many or twice as many as petals:
3. Mimoseae:
Anthers glandless. Mimosa.
4. Adenanthereae:
Anther in bud crowned by a gland, seed endospermic. Prosopis, Neptunia.
5. Piptadenieae:
Anther usually glandular, rarely without a gland; seeds without endosperm. Piptadenia, Entada.
B. Calyx imbricate:
6. Parkieae:
Parkia – flowers in heads.