In this article we will discuss about the classification of Sapindales. According to Engler, Sapindales consists of six families:- 1. Anacardiaceae 2. Auifoliaceae 3. Celastraceae 4. Sapindaceae 5. Aceraceae 6. Hippocastanaceae.
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Family # 1. Anacardiaceae:
Anacardiaceae are trees or shrubs, rarely woody vines, containing resin-passages with plenty of gum and acrid juice. Leaves are simple or pinnate, alternate, rarely, opposite exstipulate.
Inflorescence an axillary or terminal cymose panicle; flowers small and numerous, bisexual or polygamous, actinomorphic and hypogynous. Sepals 3-7, but usually 5, free or more or less connate, imbricate; petals 3-7, free or rarely connate, imbricate, sometimes absent; a cupular extrastaminal or intrastaminal disc is usually present.
Stamens double the number of petals or 10 or more in 2 whorls, free, arising from the rim of the disc. Carpels 1-5, united to form a unilocular or multilocular superior ovary, having a solitary ovule in only one of the ovary-chambers; rarely carpels free; styles 1-5, lateral or terminal and widely separated; ovule anatropous, pendulous or ascending, with dorsal raphe.
Fruit usually a drupe, rarely nut. Seeds without endosperm, with thick and fleshy cotyledons and curved embryo.
Some plants of this family are notoriously allergenic to man. The juice is pungent in most cases and very poisonous in some, e.g. Rhus species, particularly R. toxicodendron Linn, and R. venenata DC., the juice of which when applied to the skin causes erysipelas. Most species are evergreen while Spondias, Lannea, etc. are deciduous.
Leaves are ternate in Ozoroa and in some species of Rhus, but simple or pinnate leaves are found in most of the genera; leaves are alternate but in Bouea they are opposite. Cotynus coggygria Scop (Rhus cotinus Linn.) grows long hairs on the sterile part of the fruiting panicle which gets detached from the tree and is carried far by the wind.
The floral axis is a short convex receptacle with hypogynous perianth and androecium with nectaries; it is often extended in the form of a disc which is cupular or cushion-like and intrastaminal as in Rhus, or thick and extrastaminal as in Mangifera, or elongated to form a gynophore as in Melanorrhoea. Pistacia has one whorl of perianth which is sepaloid in staminate flowers and in pistillate flowers small and scarious.
Calyx deciduous in Semecarpus, and persistent in Rhus, Lartnea, etc., Petals are accrescent in Suritonia and remain attached to the fruit. In Anacardium there are 8-10 stamens of which some are fertile and some sterile, and one fertile stamen is much longer than the rest. In Mangifera there are 1 fertile and 4 sterile stamens.
In Mangifera and Anacardium ovary is monocarpellary; in Buchanania there are 5 free carpels only one however, has an ovule. Drimycarpus has inferior ovary. Styles are united or free and usually terminal but in Mangifera and Anacardium it is lateral, in Lannea the 4 free styles are perisistent. Ovary when polycarpellary and syncarpous is usually 1-celled but 4-5-celled in Spondias.
Fruit is an one-seeded drupe in most genera but in Spondias there are 4-5 seeds inside the stone. The fruit is a nut in Anacardium and is situated on a pyriform fleshy mass derived from the accrescent disc and top of pedicel. In Semecarpus similar fleshy mass is formed from the accrescent disc and calyx-base but the fruit is a drupe.
The typical floral formula for the family is:
In Anacardiaceae the stem anatomy shows that the peri cycle is made up of arc-shaped isolated strands of fibres, rarely of continuous sclerenchymatous ring. Vessels are with simple perforation plates and intervascular pitting is alternate. Fibres are septate and parenchyma cells in the wood are paratracheal. The resin canals and cells are present in all parts, in primary phloem and in many cases even in the pith.
The family contains about 600 species under 77 genera distributed in the tropical and subtropical regions of the world. It is represented in India by 65 species of which Mangifera indica Linn, is best known. Rhus a genus with 120 species and widely spread over the subtropical and temperate regions of the world from America to Japan has several species in the Himalayas at lower altitudes.
Buchanania, Semecarpus, Holigama Swintonia, Lannea etc. are other genera common in the plains. Rhus punjabensis Stew, and Pistacia integerrima Stew, grow in the W. Himalayas up to an elevation of 2500 mtr. while, Rhus khasiana Hook, grows in the Khasi hills.
Many species of this family are of economic importance. Mangifera indica Linn, produces the delicious Mango-fruits and for this reason is cultivated on a large scale all over India and other tropical countries. Anacardium occidentale Linn, is the Cashew nut tree, original of Brazil, now cultivated in India and other tropical countries; the fleshy pedicel of the ripe fruit is also edible.
The pericarp of the nut yields an oil which is very poisonous. Pistacia vera Linn, of W. Asia and- Mediterranean region is also much cultivated for the seeds which are the Pistaceo nuts of commerce. Seeds of Buchanania lanzan Spr. the Piyal tree are also used similarly as a substitute of pistaceo nut and are called Chiranjee.
Fruits of Spondias pinnata (L. f.) Kurz is the Amara or Hog-plum of India while S. purpurea Linn, and S. mombin L. are Hog-plums of Brazil and W. Indies. Kafir plum is the fruit of Harpehyllum caffrum Bernh. of S. Africa. Pistacia lentiscus Linn, yields a mastic resin while P. terebinthes L. yields turpentine.
Semecarpus anacardium LI f. the Marking-nut tree, (Hindi-Bhilwa, Bhela) exudes a juice from the ripe fruit that stains cotton a permanent black. Resinous juice of Rhus styphina Linn., R. glabra L., R. coriaria Linn. etc. is used for tanning. R. vernicifera DC. of Japan yields lacquer. R. succedanea Linn, yields Japanese wax when the berries are crushed. R. toxicodendron Linn., and R. venenata DC. are very poisonous.
Galls formed on Rhus khasiana Hook. f. and Pistacia integerrima Stew, called Karkatashringi or Kakra shinga are used by Hakims and Kahirajes in India. Timbers obtained from Mangifera indica Linn., Swintonia floribunda Griff, etc. are valuable.
Almost all workers on phylogeny of Angiosperm trace the affinity of Anacardiaceae with Sapindaceae and place Anacardiaceae in Sapindales. It is however closely related to Aceraceae, Hippocastanaceae, Sapindaceae, Simarubaceae, Meliaceae, Cneoraceae, Burseraceae and Rutaceae and more so to the last tw6 families possessing special type of resin ducts.
The family is divided into 5 tribes as noted below:
I. Mangiferae:
Leaves simple; carpels 1-6. Mangifera, Buchanania.
II. Spondieae:
Leaves pinnately compound; carpels 4-5, ovules as many as carpeles; Spondias, etc.
III. Rhoideae:
Leaves usually pinnate; carpels 4-5, ovary free from floral axis, ovule only one; Rhus, Pistacia, etc.
IV. Semecarpeae:
Leaves simple; ovary is adnate to and sunken in the thalamus Semecarpus, etc.
V. Dobineae:
Leaves pinnate; perianth absent; carpel only one: Dobinea, Compylopetalum, etc. Many modern taxonomists raise the tribe Dobineae to a distinct family Podoaceae and the genus Pistacia to a family of its own as Pistaciaceae.
Family # 2. Aquifoliaceae:
Aquifoliaceae are trees or shrubs, evergreen or deciduous, leaves are simple, alternate, exstipulate or with minute stipulates, coriaceous or chartaceous. Inflorescence axillary, cymose, very rarely flowers solitary. Flowers small and inconspicuous, bisexual or often unisexual, hypogynous. Sepals 3 — 6, usually united at the base, imbricate, persistent. Petals 4-5, or more, free or united at the base, imbricate or valvate.
Stamens equal to the number of petals or more; filaments often adnate to the petals; anthers bilocular, dehiscing longitudinally. Disc absent. Ovary superior, 4- or more-celled; ovules 1—2 in each cell, pendulous, anatropous; style short or absent; stigma lobed. Fruit a drupe, usually of 4 pyrenes. Seeds with copious fleshy endosperm and small straight embryo with superior radicle.
In the genus Nemopanthus 2 types of shoots occur, viz., long shoots and short shoots. In this genus petals are completely free. In Byronia stamens and carpels are much more in number than petals. Species of Ilex have typical tetrameroses flowers and unisexual in some cases. I. aquifolium Linn, is dioecious.
The family contains 4 genera of which Ilex consists of about 400 species. Others have only few each. These are distributed in the temperate and subtropical parts of the world. In India, the family is represented by 17 species of Ilex, common among them are 1. insignis Hook, f., I. dipyrina Wall., I. malabarica Bedd. etc.
Aquifoliaceae is allied to Gelastraceae having flowers often tetramerous and the endosperm fleshy. The family is splitted into two by some workers as Aquifoliaceae and Phellinaceae. This includes only one genus Phellie having exstipulate leaves, flowers in spikes and petals valvate.
Ilex aquifolium Linn, is the Holly, the leafy twigs of which are much in demand for Christmas decoration. Many south American species of Ilex contain caffein and I. paraguensis St. Hill is the Yerba mate, the leaves of which are used as substitute for tea. Otherwise the family is not of much importance economically.
Family # 3. Celastraceae:
Celastraceae are trees or shrubs, rarely lianas. Leaves are simple, alternate or opposite, often stipulate; stipules small and caducous. Inflorescence a cyme or cymase panicle, axillary or terminal. Flowers are very small, usually bisexual actinomorphic, hypogynous, or more or less perigynous. Calyx 4—5-lobed, often persistent, lobes imbricate, often free very near to the base.
Corolla of 4—5 free petals, imbricate or rarely valvate. A well-developed flat or cupular disc is always present. Stamens as many as an alternate to the petals, rarely double that number, inserted below or upon the disc or on its margin; anthers bithecal, dehiscing longitudinally.
Ovary superior or semi-inferior, of 2 —5 united carpels, 2—5.celled; style short, stigma lobed or capitate; ovules 2 in each cell, erect anatropous. Fruit it berry or a capsule or dry and indehiscent; seeds arillate with fleshy endosperm; aril coloured.
The disc secretes nectar. In some species a few flowers are functionally male while others remain perfect, the plants thus becoming polygamous. The aril of seeds in some genera are of micropylar origin.
The family with about 475 species under 45 genera are found in tropical and temperate countries of the world. It is well represented in India, more in the hills while a few occur also in the plains. Common Indian plants are: Euonymus indicus Heyne, E. crenulatus W. &. A. , Microtropis ramiflora Wt., Lophopetalum wiehtianum Am., Celastrus paniculata Willd., Gymnospoia wallichiana Spreng., etc.
Cellastraceae is allied to Aquifoliaceae, Stachousiaceae and Icacinaceae, having ovules with dorsal raphe, presence of a prominent disc, usually one whorl of stamens and fleshy endosperm. It is also related to Empetraceae and Salvadoraceae to some extent.
A few plants of the family are important having medicinal properties. Euonymus europaeus Linn, have seeds which are purgative and emetic. Catha edulis Forsk have leaves, with stimulant properties. The seeds of Celastrus paniculata Willd. cure rheumatism.
Family # 4. Sapindaceae:
Sapindaceae are trees or shrubs, sometimes tendril-climbers; the tendrils being the flowerless branches of the inflorescence. Leaves are alternate, usually pinnately compound, rarely ternate and very rarely simple; exstipulate or in climbing species often stipulate; stipules when present small and usually deciduous. Inflorescence is usually a cymose panicle or a thyrsus.
Flowers are small, regular or obliquely zygomorphic, bisexual or unisexual or polygamous, pentamerous or rarely tetramerous, hypogynous. Galyx usually of 5 free sepals or in regular flowers sepals 4 due to union of 3rd and 5th sepals; sepals imbricate. Corolla usually of 5 petals but 4 in actinomorphic flowers as a result of suppression; petals free, imbricate, usually with a scale-like or hairy appendage at base.
Stamens 8 or 10 in 2 whorls, free, often eccentric. An extrastaminal disc is usually present; the disc is unilateral or annular, often represented by glands.
Ovary tricarpellary syncarpous, 3-locular, superior, lobed or not; style terminal; ovules 1-2 in each loculus, ascending with ventral raphe. Fruit dry or fleshy; dry fruit may be a capsule or nut and fleshy fruit a drupe or berry. Seeds usually arillate, without endosperm and with curved embryo.
Cardiospermum is a herbaceous climber but Serjania, Paullinia, etc. are lianas; they climb by tendrils which are metamorphosed sterile branches of the inflorescence coiled like watch-spring. Sapindtis, Aphania, Litchi, etc. have actinomorphic flowers, while, Erioglossum, Cardiospermum, etc. have zyogomorphic flowers with eccentric androecium.
In many cases the apparent bisexual flowers are functionally female having stamens with anthers that do not open and pollens do not germinate. Schleichera, Dodonae a etc. have flowers apetalous. Stamens are usually 8, but in Turpinia there are 5 stamens and Deinbollia has numerous stamens.
Anomalous condition is observed in the stems of woody climbers as well as of some erect genera where groups of fibro-vascular structures are distributed outside the central cylinder.
In some cases the central vascular ring is lacking and there are several rings of xylem and phloem, or the central wood mass divides into three or more portions which grow in thickness separately. Vessels are small, perforations simple and neurovascular pitting alternate. Xylem parenchyma is usually paratracheal. Pericycleorms a continuous ring of fibres.
The floral formula for a hermaphrodite flower is:
Sapindaceae with about 900 species under 92 genera is distributed in almost all tropical countries of the world. The family is allied to Anacardiaceae, Aceraceae and Hippocastanaceae, the last 2 families being formerly included in Sapindaceae.
It is also related to Simarubaceae, Burseraceae, Cneoraceae, Fulianaceae, Meliaceae and Rutaceae to some extent, it resembles the family Euphobiaceae having ovule usually 1 in each cell, ventral raphe, tricarpellary ovary, arillate seeds and often unisexual flowers.
The family is divided into 2 subfamilies:
I. Sapindoideae:
(Eusapindaceae) Ovule solitary in each cell, erect or ascending, with downward micropyle.
(i) Nomophyllae—Leaves usually imparipinnate, disc oblique,—Serjania, Erioglos- sum, etc.
(ii) Anomophyllae—Leaves usually paripinnate, disc annular—Sapindus, Schleichera, etc.
II. Dodonaeideae (Dyssapindaceae):
Ovules 2 or more in each cell, erect or pendulous or horizontal, rarely 1 and pendulous, with upward micropyle—Dodonea, Harpullia, etc.
The economic importance of the family lies in the fact that several species yield edible fruits which are very delicious, e.g. Litchi chinensis Sonner. the Litchi of E. Asia, Nephelium lappaceum Linn., the Rambutan of Malaya, Melicocca bijuga Linn., of W. Indies, Blighia sapida Koen.—the Akee of Guinea, Dimocarpus longan Lam—the Longan (Beng. Anshphal), etc.
Schleichera oleosa Merr. also yields edible fruit but is more important being the best tree for rearing lac insects. The timber of this tree is also valuable and the seeds yield an oil used for cooking and burning and is the macassar oil of the hair dressers. Sapindus saponaria Linn., S. mukorossi Gaertn. and S. trifoliatus Linn, produce berries the epicarp of which is widely used as a substitute for soap for washing woolen clothes.
Family # 5. Aceraceae:
Aceraceae are trees or shrubs, deciduous. Leaves are opposite, simple, palmiveined, entire or lobed, or leaves compound, exstipulate. Inflorescence is a raceme, rarely corymbose or fasciculate. Flowers are small, regular, polygamous or diocious or only hermaphrodite, dich- lamydious hypo- or perigynous, 5-4-merous. Sepals 4-5, free or connate at base, imbricate. Petals 4-5, free, imbricate, sometimes absent.
Extrastaminal disc is usually present, annular or lobed, or reduced to teeth. Stamens 8 in 2 whorls, rarely 10, very rarely less than 8, hypogynous or perigynous or rarely inserted on the margin of the disc; anthers bilocular, introrse, dehiscing longitudinally; rudimentary gynoecium usually present in male flowers.
Ovary usually superior, bicarpellary syncarpous, bilocular, laterally compressed; ovules 2 in each locule orthotropous or anatropous, superposed or colateral on axile placentation, with dorsal raphe; styles 2, free or united below.
Fruit a schizocarp of 2 winged nut-like fruitlets separating into 2 samaras when ripe. Seed solitary in each fruitlet, exalbuminous and with curved embryo and thin folded or rolled rarely flat cotyledons.
Most species have simple leaves, lobed or not; some species of Acer and Dipteronia have 3-foliolate or 5-foliolate leaves. The racemes have the male flowers in the lower portion and bisexual flowers in the apical portion.
Flowers are apetalous in Acer grandi- dentatum DC. and A. carpinifolium Linn. In A. rubrum Linn, stamens are in one whorl. In some species of Acer carpels are more than 2. Sometimes the seeds have more than 2 cotyledons.
The wood anatomy shows the vessels to be small, with spiral thickenings and simple perforations. Wood parenchyma is absent or almost so; fibres are short and simple pitted and medullary rays are homogeneous. The flowers are entomophilous or anemophilous.
The floral formula may be expressed as:
The family consists of about 200 species under 3 genera distributed mainly in the temperate regions of the northern hemisphere. It is represented in India by 15 species of Acer occurring in the Himalayas and Khasi hills. Fossil remains of Acer were discovered belonging to the Tertiary period.
The family is economically important for the fact that a few species yield good timber and that of the sycamore tree—Acer pseudoplatanus Linn, is hard and durable. A. saccharum Marsh and A. nigrum Michx. are the Sugar-maples reputed for yield of a sweet sap. Many species of Acer are cultivated as avenue trees and as garden-ornamentals.
The family is closely related to Sapindaceae and Hippocastanaceae and also to Anacardiaceae and Simarubaceae to some extent. It is allied also to Burseraceae, Cneoraceae, Julianiaceae, Meliaceae, Rutaceae on one side and Hamamelidaceae and Altingiaceae on the other.
Family # 6. Hippocastanaceae:
Hippocastanaceae are deciduous trees with large winter buds covered with resinous scale-leaves. Leaves with a long petiole and a palmately compound blade, opposite, exstipulate, hairy when young.
Inflorescence is a thyrsus type of panicle, terminal. Flowers are polygamous, obliquely zygomorphic; male flowers in the upper part of the inflorescence and the bisexual flowers in the lower part. Sepals 5 united, lobes valvate.
Petals 5 or 4, free, imbricate. Stamens 8-5; inserted on a disc; anthers introrse; disc is often one-sided. A rudimentary ovary present in male flowers.
Bisexual flower with a superior, tricarpellary syncarpous, 3-locular ovary; ovules 2 in each loculus, superposed, upper with dorsal raphe and lower with ventral raphe; style one. Fruit 3-valved leathery capsule often spiny, usually with one seed. Seeds exalbuminous, with united cotyledons and the radicle lying in a fold of the testa.
The small family consists of 2 genera and 15 species occurring in the north temperate regions as well as in Mexico and S. America. Aesculus indica Hook-occurs in the W. Himalayas while A. assamica Griff, grows in E. Himalayas and Naga Hills and comes down to the plains of northern Bengal. The family is not of much economic importance. It is very close to Sapindaceae in which it was previously included.