1. Nyctaginaceae:
Plants—usually herbs or shrubs (e.g., Mirabilis), sometimes climbers (e.g., Bougainvillaea, Pisonia). Leaves—usually opposite, simple, entire, more or less unequal, exstipulate. Inflorescence— cymose. Flowers—regular, usually bisexual (unisexual in Pisonia), hypogynous with involucre. Perianth—5, usually petaloid, united (tubular or funnel-shaped), the lower part inflated and persistent in fruit forming anthocarp.
Stamens—usually 5-8, unequal. Carpel—one; ovary superior, 1-celled with basal, anatropous or campylotropous ovule. Fruit—achene, enclosed in the perianth base. Seed—albuminous, with mealy perisperm. Embryo—curved or folded, with broad leaf-like cotyledons and an inferior radicle.
This family consists of 28 genera and about 250 species which are found both in tropical and subtropical regions.
Common plants of nyctaginaceae:
(1) Marvel of Peru or Four o’clock plant (Mirabilis jalapa L.), a well-known ornamental shrub.
(2) Boerhaavia repens L. and B. diffusa L. are common weeds.
(3) Bougainvillaea spectabilis Willd., a handsome climber with 3 brightly coloured bracts, often planted in gardens.
(4) Pisonia aculeata L., a large spinous straggling shrub.
This family is closely allied to Polygonaceae but readily distinguished by the sepaloid bracts, unicarpellate ovary, and the peculiar fruit enclosed in the persistent base of the perianth (anthocarp).
This family is of little importance economically. Boerhaavia is used in medicine. Some plants are used as ornamentals, such as, Mirabilis, Bougainvillaea, Abronia, etc.
2. Basellaceae:
Plants—perennial scandent herbs with succulent stems. Leaves—alternate, simple, fleshy, ex-stipulate. Inflorescence—spike or raceme.
Flowers—small, regular, incomplete, bisexual, hypogynous. Perianth—represented by 5 sepals, white or reddish, more or less united at the base, subtended by a pair of bracts forming an involucre, imbricate, persistent. Stamens—5, antisepalous, united with the bases of the sepals. Carpels—(3); ovary superior, 1-celled with solitary, campylotropous ovule or basal placenta; style 1; stigma usually 3-fid. Fruit—drupe invested by the persistent perianth. Seeds—with scanty endosperm and a rolled embryo.
This family consists of 5 genera and about 22 species which are commonly found in the tropics.
Common plant of basellaceae include:
Basella rubra L., shoots of which are taken as spinach.
This family is readily distinguished from other members of Centrospermae by the scandent succulent character, bisexual apetalous flowers, fleshy persistent perianth leaves enveloping the fruit, and spirally twisted embryo. Bentham and Hooker included this family under Chenopodiaceae, but it differs from the latter by the biseriate perianth. It is related very closely to Portulacaceae and it is believed it arose as an offshoot of the latter.
This family is of little economic importance. The shoots of Basella are taken as spinach. The tuberous roots of Ullucus tuberosus are eaten in America as a substitute for potato. The Madeira vine (Boussingaultia) is an ornamental garden plant.
3. Portulacaceae:
Plants—usually annual or perennial herbs. Leaves—opposite or alternate, entire, succulent, usually stipulate (scarious stipules). Inflorescence—cymose or racemose. Flowers—regular, bisexual, hypogynous without disc. Sepals—usually 2, placed antero-posteriorly, imbricate. Petals—usually 4-6, free.
Stamens—4-6 or more, anti- petalous and united with the petals at the base. Carpels—(2-3), ovary superior (half-inferior in Portulaca), sunk in torus, 1-celled with 2 to many campylotropous ovules on a central basal placenta; styles and stigmas 2-5. Fruit—capsule, dehiscing circumscissilely. Seed— albuminous. Embryo—curved.
This family consists of 16 genera and 500 species which are generally distributed in tropical and temperate regions.
Common plants of portulacaceae include:
(1) Purslane (Portulaca oleracea L.),
(2) P. quadrifida L. and
(3) P. tuberosa Roxb. are very common weeds growing in nooks and corners.
This family is closely allied to Caryophyllaceae but readily distinguished by succulent leaves, number of sepals and stamens, and 2-5 styled 1-celled ovary with campylotropous ovules on a basal central placenta. It is also closely related to Basellaceae; the genus Portulaca establishes a link between them. It is also related to Aizoaceae.
This family is important economically from the domestic point of view. They are used as ornamentals. Portulaca grandiflora L. can be best cited as an ornamental plant. The herbage produced by P. oleracea is useful to certain extent as a pot-herb and green salad.
4. Nymphaeaceae:
Plants—annual (e.g., Euryale) or perennial aquatic herbs with cauline (e.g., Cabomba) or rhizomatous stems embedded in the mud. Leaves—often floating (submerged in Nelumbium), peltate or cordate, on long petioles (but sessile in Cabomba).
Flowers—solitary, usually on a scape, large and showy, regular, bisexual, hypogynous to epigynous (e.g., Euryale), acyclic, hemicyclic, or cyclic. Sepals—3-6, or adnate to the torus. Petals—3 (e.g., Cabomba) to numerous, often gradually passing into stamens, imbricate.
Stamens—3-6 (e.g., Cabomba) or numerous; filaments foliaceous. Carpels—3-many, united into a many-celled ovary (e.g., Nymphaea and Nuphar) or free and sunk in spongy thalamus (e.g., Nelumbium); ovary superior or inferior (e.g., Victoria and Euryale); ovules 1 to many on the inner walls or from the apex of the carpels.
Fruit—a follicle (e.g., Cabomba), or aggregate of achenes (e.g., Nelumbium) or spongy berry (e.g., Euryale). Seeds often arillate, generally with both perisperm and endosperm, and a straight embryo.
This family consists of 8 genera and about 90 species which are cosmopolitan.
The chief constant floral characters of the family are spirocyclic, regular, bisexual flowers or rarely cyclic with gradual change from sepals to petals and to stamens.
This, family has got wide variation in the construction of floral parts. The variation occurs mainly due to number of sepals and petals, nature of thalamus, apocarpy or syncarpy.
This family has been sub-divided into 3 sub-families based on the floral range and construction of floral parts.
Subfamily 1. Cabomboideae:
The subfamily is represented by the genus Cabomba, which consists of 6 perianth-leaves in two whorls 3 + 3, the outer one forms the calyx and the inner one corolla. Stamens 6. Carpels 3, free. Flowers are cyclic, trimerous and hypogynous.
Subfamily 2. Nelumboideae:
The subfamily is represented by the only genus, Nelumbo, which consists of indefinite perianth leaves, the outer whorl of 5 sepals. Stamens indefinite. Carpels free, numerous, spirally arranged. Flowers are spirocyclic and hypogynous.
Subfamily 3. Nymphaeoideae:
This subfamily is represented by the most prominent genus Nymphaea. It consists of 4-5 sepals in whorls and indefinite petals; stamens indefinite; carpels numerous, fused. Flowers are spirocyclic, hypo-, peri-, or epigynous (e.g., Euryale).
Common plants of nymphaeaceae include:
(1) Water-lily or Pond-lily (Nymphaea lotus L.), Nymphaea pubescens Willd.
(2) Red water-lily (Nymphaea rubra Roxb.).
(3) Blue water-lily (Nymphaea stellata Willd.).
(4) Lotus (Nelumbium speciosum Willd. = Nelumbo nucifera Gaertn.).
(5) Euryale ferox Salisb., commonly found in the tanks of Bangladesh, all parts of which are beset with prickles.
(6) Yellow water-lily (Nuphar luteum L.).
(7) Cabomba aquatica, commonly cultivated in the aquarium.
This family bears relationship with Papaveraceae in the character of superficial placentation of the ovary and large peltate-rayed stigmas. It is allied to Magnoliaceae in the character of accessory whorls and stamens.
It also established a close link with Alismataceae in the structure of the ovary. Nymphaeaceae is readily distinguished by the aquatic habit, usually long-petioled peltate leaves and long-peduncled flowers, and parietal or superficial placentation.
This family has very little economic importance. Many plants have medicinal value. Fruits and rhizomes of many species are edible. Most plants are cultivated as ornamentals.
5. Anonaceae:
Plants—trees or shrubs, sometimes woody climbers (e.g., Artabotrys). Leaves—alternate, simple, entire, gland-dotted, exstipulate. Flowers—solitary, regular, usually bisexual, hypogynous, spirocyclic, trimerous. Sepals-3, small, usually free or united below valvate.
Petals—6 (in two series) or 3 (e.g., Anona), valvate or imbricate (e.g., Uvaria). Stamens—numerous, spirally set on a slightly elongated convex thalamus; filaments short and thick; anthers linear with prolonged truncate connective, extrorse.
Carpels—usually numerous, free and spirally set on the thalamus, ripe carpels indehiscent; ovary superior, 1-celled; ovules usually numerous in a double row on the ventral suture of the carpel; style short or absent. Fruit—an etaerio of drupes, but in Anona the ripe carpels are fused together forming a large fleshy fruit (composite berry). Seed—often arillate with ruminated albumen and a minute embryo.
This family consists of about 80 genera and 850 species which are widely spread in the tropics.
Common plants of anonaceae include:
(1) Custard apple (Anona squamosa L.).
(2) Bullock’s heart (Anona reticulata L.).
(3) Polyalthia longifolia Benth. & Hook, f., an ornamental tree whose foliage is largely used for decorative purpose on festive occasion.
(4) Polyalthia cerasoides Benth. & Hook., a tree commonly found in the thickets.
(5) Artabotrys odoratissimus R. Br. = A. uncinatus Merr , a hook climber which is usually cultivated in gardens for its fragrant flowers.
(6) Uvaria macrophylla Roxb.= Fissitigma macrophylla Merr., a woody climber found in Bangladesh.
(7) Cananga odorata Hook. & Thorns. = Desmos chinensis Lour., a small tree often planted in gardens.
This family shows an affinity with Magnoliaceae but ruminate endosperm, valvate corolla, prolonged connective, and exstipulate leaves separate it from the latter. The trimerous flower and small embryo establish a close relationship with monocotyledons.
This family is of some economic importance. Anona squamosa and A. reticulata yield sweet and fleshy edible fruits. Species of Polyalthia are grown as ornamental trees; its wood is used for making masts.
6. Lauraceae:
Plants—trees or shrubs (excepting Cassytha, a twining parasitic perennial herb), with aromatic bark and foliage. Leaves—usually alternate, simple, entire, coriaceous, gland dotted, mostly curviveined (but in Cassytha reduced to scales or absent), exstipulate. Inflorescence— raceme, spike, umbel or panicle.
Flowers—small, greenish or yellowish, regular, bisexual (sometimes unisexual), hypogynous, trimerous. Perianth—3 + 3, more or less united at the base, sepaloid, persistent, imbricate. Stamens—12, usually in 4 whorls of 3 stamens each, generally the innermost is reduced to a whorl of staminodes (e.g., Cinnamomum), the third whorl usually bears a pair of glandular protuberances, inserted to the perianth tube; anthers 2-4-celled, usually with valvular dehiscence.
Carpel—1; ovary superior, 1-celled with 1 anatropous pendulous ovule, placentation marginal. Fruit— drupe, sometimes berry and more or less enveloped by the cup-shaped receptacle, and sometimes also by the persistent base of the perianth (e.g., Cassytha). Seed—exalbuminous with large straight embryo.
This family contains about 45 genera with 1,100 species, distributed in the tropical and subtropical regions.
Common plants of lauraceae include:
(1) Cryptocaria floribunda Nees., a tree.
(2) Beilschmiedia roxburghiana Nees., a deciduous tree.
(3) Camphor tree (Cinnamomum camphora Nees.), yields camphor.
(4) C. tamala Nees., a medium tree, the leaves of which are used as a spice in cooking.
(5) Cinnamon (C. zeylanicum Breyn.), a small tree, the bark of which is used as a spice.
(6) Cassytha filiformis, a common leafless thread-like greenish parasite.
(7) Dehassia kurzi King, an evergreen tree, commonly found in Bangladesh.
(8) Machilus vilosa Hook, f., a large tree.
(9) Phoebe lanceolata Nees., an evergreen tree grows at the foot of East Himalayas.
This family is readily distinguished from allied families by the presence of small undifferentiated perianth, trimerous stamens in several whorls, valvular dehiscence of anthers, drupe-like fruit and single exalbuminous seed with large straight embryo.
The family is economically important. Many plants yield aromatic oils. Camphor is obtained from Cinnamomum camphora; C. tamala and C. zeylanica yield spices. Some plants of this family, viz., Persea, Sassafras, etc., yield fragrant wood for cabinet work. Persea americana yields a kind of edible fruit (Avocado pear). A few species are ornamentals.
7. Magnoliaceae:
Plants—shrubs or trees. Leaves—alternate, simple, coriaceous, entire, stipulate. Flowers—solitary, terminal or axillary, usually bisexual (rarely unisexual, e.g., Drimys, Schizandra), regular, hypogynous; hemicyclic or acyclic, trimerous; thalamus convex or elongated. Perianth—consists of 9 or more free petaloid parts, or the 3 outer ones green, arranged in whorls, hypogynous, imbricate.
Stamens—usually numerous, free, spirally arranged on the lower portion of the floral axis (androphore). Carpels—numerous, free, spirally arranged on an elongated conical floral axis (gynophore), ripe carpels dehiscent; ovary superior, 1-celled; ovules 2 to many, anatropous on the ventral suture. Fruit—aggregate (follicle) or berry. Seeds—pendulous, suspended for a time by slender threads, one or few, with a copious endosperm and a small embryo.
This family consists of 10 genera and over 100 species, which are found mostly in the tropics but a few may be found in the temperate zone.
Common plants of magnoliaceae include:
(1) The Champak (Michelia champaca L.),
(2) Magnolia pterocarpa Roxb.,
(3) Magnolia grandiflora, L., all of which produce fragrant flowers and for this reason are cultivated in the gardens.
(4) Magnolia campaellii, a shrub producing beautiful flowers can be found in Darjeeling.
This family is considered to be as most primitive among the dicotyledons. The primitive character is exemplified by spiral arrangement of stamens and carpels, and apocarpous pistil. It also establishes a close link with gymnosperms.
The gymnospermous character of wood, i.e., tracheids with bordered pits, has been revealed in the genus Drimys. It has been presumed by some authors that the elongated floral axis of a Magnolia, which bears numerous spirally arranged free sporophylls indicate a probable relationship with Bennettites, a genus of Bennettitales, particularly in the presence of sporophyll-bearing axis of the same.
Magnoliaceae is also allied to Anonaceae from which it is readily distinguished by having imbricate corolla and uniform albumen. The family is characterized by the stipulate leaves, bisexual flower, numerous stamens and carpels spirally arranged on an elongated floral axis (torus).
The characteristic monocolpate pollen grains of the ‘Magnolian’ families perhaps stands parallel to monocots and indicates that the monocots are more closely related to the ‘Magnolian’ dicots rather than the ‘Ranalian’ dicots.
Economically, the family is not very much important with the exception of the flowers of many species of Magnolia and Michelia, as they are handsome, showy and fragrant. Michelia champaca has medicinal value. The species of Drimys, particularly its bark known as Winter’s bark, is used in medicine.
The fruit of Illicium verum Hook. f. is sometimes used for medicinal purpose. The wood of Liriodendron, Michelia excelsa Bl. and several species of Magnolia is used in making furniture and cabinet work. Species of Magnolia, Michelia, Liriodendron (tulip tree), Talauma are grown in gardens as ornamental plants.
8. Papaveraceae:
Plants—generally annual herbs (rarely shrubs, e.g., Dendromecon) with milky or coloured latex. Leaves—alternate, simple, entire or more often lobed or much divided, exstipulate. Inflorescence—racemose or cymose. Flowers—bisexual, regular, hypogynous. Sepals—2 (sometimes 3), free, caducous, imbricate. Petals—usually 2 + 2 (sometimes 3 + 3), absent in Macleaya, crumpled, deciduous.
Stamens —numerous, in several alternating whorls (generally multiple of 2 or 3); anther bilocular. Carpels—2-many, syncarpous; ovary superior 1-celled, with numerous anatropous or campylotropous ovules on parietal placentae, (but basal placentation in Bocconia) or many-celled; stigma radiating from the centre, either sessile or supported on a distinct style. Fruit—capsule, opening by apical pores or valves. Seeds —with oily endosperm and a minute embryo.
This family consists of 28 genera and about 250 species which are usually found in the North temperate zones.
Common plants of papaveraceae include:
(1) Opium poppy (Papaver somniferum L.), only white-flowered forms are commonly cultivated for obtaining opium.
(2) Mexican poppy or Prickly poppy (Argemone mexicana L.), a prickly erect herb with yellow flowers which grows wild on roadsides and rice-fields.
(3) Oriental poppy (Papaver orientate L.) and
(4) P. argemone L. are common garden annuals.
(5) Meconopsis nepalensis DC. and M. wallichii Hook., are the commonly occurring plants in Darjeeling at a varying altitude of 8,000-11,000 ft.
This family differs from Ranunculaceae by dimerous calyx, syncarpous ovary and milky or coloured latex. It forms a link with Cruciferae and Capparidaceae in the character of dimerous arrangement of the accessory sets and pod-shaped ovary, but differs from them in the character of the seed, and narcotic milky latex.
It is also allied to Nymphaeaceae in the general structure of the flower. Papaveraceae is characterized by caducous calyx, usually crumpled corolla, numerous stamens in several whorls, unilocular ovary with parietal placentation and capsule fruit.
Papaveraceae is economically important. The opium of commerce is obtained from the dried latex of unripe capsules of Papaver somniferum; an alkaloid known as ‘morphine’ is obtained from it. Chelidonium majus L. and Sanguinaria canadensis L. are medicinal plants. Some ornamental plants belong to the family.
About 20 genera especially the oriental poppy (Papaver orientale), californian poppy (Eschscholtzia sp.), blue poppy (Meconopsis sp.), prickly poppy (Argemone mexicana), etc., are useful for decorative purposes.
9. Mimosae:
Leaves—usually bipinnate. Flowers—in spikes, regular, usually 4-merous, less frequently 5- or 3-merous. Petals—4, united or free, valvate in aestivation. Stamens—numerous, sometimes definite, exerted. Embryo—straight.
Common plants of mimosae include:
(1) Sensitive plant (Mimosa pudica L.), a common straggling herb.
(2) The Babul or Gum tree (Acacia arabica Willd.), a small tree which yields gum.
(3) Cutch tree (Acacia catechu Willd.), the wood of which on distillation produces ‘cutch’ of commerce.
(4) Acacia moniliformis Griseb., commonly planted on roadsides and parks and bears phyllodes.
(5) Acacia recurva also bears phyllodes, common in Darjeeling.
(6) Silk flower (Albizzia lebbek Benth.), commonly planted on roadsides.
(7) Entada scandens Benth. = E. phaseoloides Merr., a woody climber with snake-like branches, the seeds of which- are used for curling garments.
(8) Neptunia oleracea Lour and N. plena Benth., common water-weeds with sensitive leaves.
(9) Prosopis spicigera L.
(10) Xylia dolabriformis Benth., Iron wood tree of Burma.
(11) Manila, tamarind (Pithecolobium dulce Benth. = Inga dulcis Willd., a medium tree, common.
(12) Rain tree (Enterolobium saman Prain = Samanea saman Merr.), an avenue tree.
(13) Red wood (Adenanthera pavonina L.), a tree.
This subfamily is allied to Rosaceae but readily distinguished by the hypogynous stamens, position of odd sepal and nature of the fruit.
The plants of this subfamily possess mucilaginous juice and astringent properties. Gum tree and Cutch tree are the most important plants. Xylia is a valuable timber tree.
10. Crassulaceae:
Plants—annual or perennial herbs or under-shrubs with succulent stems. Leaves—alternate, sometimes opposite or whorled, simple, entire but sometimes lobed, succulent, usually persistent, ex-stipulate.
Inflorescence—usually cymose, sometimes spike or panicle. Flowers —regular, bisexual (sometimes unisexual), hypogynous. Sepals—4, sometimes 5, free (but united in Kalanchoe), valvate or imbricate. Petals—4, sometimes 5, free, valvate or imbricate. Stamens—as many as or twice as many as the petals in two whorls, situated on a swollen or cup-like disc, free.
Carpels—usually equal to the number of petals, free or united below, each usually subtended by a scale-like nectar gland at the base; ovary superior, 1-celled with parietal placentation. Fruit —follicle. Seeds—with fleshy endosperm and straight embryo.
This family consists of 30 genera with about 1,300 species, which are widely distributed in the world excepting Australia and Oceania.
Common plants of crassulaceae include:
(1) Bryophyllum calycinum Salisb., a stout fleshy herb.
(2) Kalanchoe heterophylla Prain, a stout fleshy herb, chiefly found in Pareshnath Hill.
(3) K. laciniata Adams., found in Bangladesh, Behar and other places.
(4) K. spathulata Adams., a common weed.
This family is readily distinguished from others by the succulent character of stems and leaves, the gynoecium composed of usually as many carpels as there are petals, a like number of stamens in each whorl and by the presence of scale-like gland at the base of each carpel.
This family is of little economic importance. Bryophyllum is used in medicine. Some are planted in our gardens as ornamentals.
No comments yet.