In this article we will discuss about the classification of Piperales. According to Engler, Piperales consists of three families:- 1. Piperaceae 2. Chloranthaceae 3. Saururaceae.
Family # 1. Piperaceae:
Piperaceae are herbs or shrubs, rarely trees, sometimes climbing with adventitious roots, usually aromatic. Leaves of Piperaceae are simple, alternate, entire, usually stipulate; stipules adnate to the petiole; leaf-blade often oblique. Flowers of Piperaceae is very small, naked, bisexual, hypogynous, bracteate, densely arranged in spikes; spikes usually fleshy and drooping.
Stamens 1- 10, in one or two whorls; filaments short with 2-celled anther; anther dehiscing longitudinally, often 1-celled due to confluence of the cells.
Ovary superior, unilocular, of 2- 5 carpels, ovule one, basal, orthotropous, rarely with one integument; style short or absent, stigmas as many as carpels, rarely feathery. Fruit a small drupe with a minute seed containing a very small embryo in copious endosperm and perisperm.
The family of Piperaceae contains about 2000 species in only 7-8 genera of which Piper has about 750 species and Peperomia over 600. The family of Piperaceae is distributed in all tropical and subtropical countries of the world. In India it is represented by 45 species of Piper and about 10 species of Peperomia.
Some species are geophyllous; in such cases during germination of seed one of the cotyledons remains inside and functions as sucker while the other is borne on the elongated hypocotyl developing into the green cotyledonary leaf. Such a geophyllous species— Peperomia umbilicata Ruiz. & Pav. has an underground, short, thick stem resembling a rhizome or tuber.
In some genera the vascular bundles are scattered in the ground tissue like that of a monocotyledonous plant. In Piper nigrum L. there are 2 rings of vascular bundles, the outer ultimately forming a continuous ring while the inner remains distinct.
The family is economically important for the genus Piper, many species of which have medicinal properties or are used as spices. Piper nigrum L. is the Black-pepper, cultivated in India and Malaya.
Piper longum L. is used medicinally and grows wild in India and Malaya and is also cultivated. Piper betle L.f. is the betle-vine, the leaves of which are chewed in the tropical Asiatic countries. Piper Chaba Hunt. Piper Cubebe L.f. are also important for their medicinal properties.
The family is closely allied to Chloranthaceae which has very small lowers, perianth absent or rudimentary, drupaceous fruit, embryo minute in copious endosperm. The two families are placed in one order Piperales by Engler as well as by Hutchinson who includes this order in his Herbaceae and traces its origin from Ranales.
On account of the scattered arrangement of vascular bundles in some members and sucker-like behaviour of one of the cotyledons some taxonomists like Hill and others suggest that the Monocotyledons have originated from Pipcraceae.
From palynological study Kuprianova comes to the conclusion that one group of Monocot families, i.e., Palmae, Araceae and Lemriaceae has been derived from Piperales. The inflorescence of Araceae bears some resemblance to that of Piperaceae but this, however, is superficial. Some taxonomists prefer to split the family into two, e.g., Piperaceae and Peperomiaceae.
According to them Peperomiaceae have the following characters:
Succulent herbs or subshrubs; exstipulate leaves; flowers hermaphrodite, in spikes, with succulent bracts; perianth absent; stamens 2, lateral, anthers finally confluent; ovary superior, monocarpellary, with one basal orthotropous ovule, stigma pilose; perisperm mealy.
Family # 2. Chloranthaceae:
Chloranthaceae is a small family of herbs, shrubs or trees, usually aromatic. Leaves of Chloranthaceae are opposite, stipulate; stipules very small, adnate to petiole; petiole-bases joined. Inflorescence is a spike or cyme, often paniculate or condensed into a head.
Flowers of Chloranthaceae is bisexual or unisexual, actinomorphic, hypogynous or epigynous, small and bracteate. Perianth absent or represented by 1-3 minute sepals, free or slightly connate at base. Stamens 1-3, often united at the base and adnate to the ovary; anther bilocular or unilocular, dehiscing laterally.
Ovary superior or inferior, of one carpel, with one pendulous ovule; stigma sessile, 2-lobed. Fruit drupaceous; seed with a small embryo in copious endosperm. In this family the vascular bundles are arranged in a ring but in the genus Sarcandra the wood is vessel-less. Floral anatomy also shows primitive character, e.g., the stamens have vascular traces.
The family is closely allied to Piperaceae, both having stipules adnate to petiole, flowers perianthless or perianth rudimentary, ovules orthotropous, drupaceous fruit, small embryo and copious endosperm. This is a small family with only 4 genera and a little over 30 species found in tropical America, Polynasia and some tropical countries but not represented in India.
Family # 3. Saururaceae:
Saururaceae is a small family of perennial herbs. Leaves of Saururaceae is simple, alternates stipulate; stipules adnate to petiole; upper leaves often coloured. Flowers of Saururaceae are small, hermaphrodite, regular, in spikes or racemes; an involucre of bracts is often present. Perianth absent, stamens 3, 6 or 85 free or adnate to the ovary; anthers extrorse or introrse.
Ovary superior or inferior, of 3-4 free or united carpels; when apocarpous with 3-4 orthotropous ovules in each carpel, when syncarpous with 6-8 or only 1 ovule in each cell on parietal placentation. Fruit of 1 -4 dehiscent cocci or in case of syncarpous ovary in- dehiscent or dehiscing apically, sometimes glochidiate.
Seed with scanty endosperm and plenty of mealy perisperm and a small embryo. The small family of 7 species under 5 genera is distributed in E. Asia and N. America. It is represented in India by a single species of a creeping herb, viz. Houttuynia cordata Thunb.