In this article we will discuss about:- 1. General Features of the Verbenaceae 2. Floral Range in the Verbenaceae 3. Position and Affinity 4. Number and Distribution 5. Commonly Occurring Plants 6. Economic Aspects.
General Features of the Verbenaceae:
Habit – Herbs, shrubs or trees.
Leaves – Opposite or whorled, simple or compound, exstipulate.
Inflorescence – Cymes or spikes.
Flowers – Bisexual or polygamous, irregular, hypogynous.
Calyx – Sepals 5, united, campanulate or tubular, persistent.
Corolla – Petals 5, united, bilabiate, tubular, imbricate.
Anoroecium – Stamens 4, didynamous or 2; staminodes often present; anthers 2-celled, dorsifixed.
Gynoecium – Carpels 2, syncarpous; ovary 4-lobed or entire, superior, 2- to 4-locular, ovules 1 or 2 in each loculus; style terminal.
Fruit – Berry or drupe.
Seeds – Erect, exalbuminous; testa thin; embryo straight.
Floral Range in the Verbenaceae:
In general, the flowers are pentamerous and irregular. The exception is Physopsis, where the flowers are tetramerous and regular.
The tendency to zygomorphy is more marked in the corolla than in the calyx. In Lantana, Lippia and others, the upper lip is formed by the union of the two upper corolla lobes. While valvate aestivation is a characteristic of the calyx, the corolla shows an imbricate aestivation.
All the four stamens may become equal and fertile. In Geunsia and Tectona, the stamens are 5 in a number. The fifth stamen is usually obsolete and may be represented by a staminode. The stamens may also become diandrous owing to the suppression of staminodes of the two posterior or anterior stamens.
The carpels are frequently 2, but 4 in Duranta and 5 in Geunsia. The posterior carpel may become abortive, as in Lantana and other genera.
The ovary may become round. It is generally somewhat lobed, the lobes being 2 in Lantana and 4 in Clerodendrum and Verbena.
Position and Affinity of the Verbenaceae:
The Verbenaceae was included in the Lamiales by Bentham-Hooker. In Engler’s arrangement, the family appeared under the suborder Verbenineae of the order Tubiflorae. Hallier retained it within the Tubiflorae and sought its origin from the Scrophulariaceae. Hutchinson at first (1926) accepted it as belonging to the Lamiales, but later (1948, 1959, 1969) segregated it as the Verbenales and derived it from rubiaceous stocks.
The Verbenaceae is related to the Labiatae by the presence of the persistent calyx, bilabiate corolla and inferior micropyle of the ovule. It is allied to the Boraginaceae by the nature of inflorescence, calyx and fruit. It bears a relationship with the Acanthaceae, but differs in having a four-celled ovary with one ovule in each cell or two-celled ovary with two ovules in each cell.
Number and Distribution of the Verbenaceae:
The Verbenaceae embraces about 75 genera and over 3,000 species. Though the members of the family are inhabitants of the tropical or sub-tropical regions, they also extend into the temperate zones.
Commonly Occurring Plants of the Verbenaceae:
White Mangrove (Avicennia alba Bl.) is a tree with long pneumatophores and viviparous seeds, being noticed in the Sunderbans.
Callicarpa longifolia Lamk. is a hedge plant and so is Duranta repens L.
Callicarpa macrophylla Vahl is seen in village shrubberies.
Clerodendrum indicum (L.) O. Kuntze is a tall shrub with hollow stems.
Clerodendrum inerme (L.) Gaertn. and C. viscosum Vent, are herbs on waste lands.
Congea tomentosa Roxb. var. azurea Clarke is a large climber.
Faradaya splendida F. v. Muell is a tall climber with showy flowers.
Candahar Tree or Comb Tree (Gmelina arborea L.) is a moderatesized tree of Orissa jungles.
Holmskioldia sanguinea Retz. and Petrea volubilis Jacq. are garden plants, the former with red flowers and the latter with blue flowers.
Lantana camara L. and L. indica var. albiflora Wt. ex Clarke are weeds.
Phyla nodiflora (L. ) Greene is a herb of moist places.
Premna obtusifolia R.Br, is a shrub of the Sunderbans and so is Stachytarpheta urticaefolia (Salisb.) Sims.
Indian Oak or Teak (Tectona grandis L. f.) is a large deciduous tree.
Chaste Tree of Indian Privet (Vitex negundo L.) is a shrub, bearing trifoliate or quadrifoliate leaves.
Economic Aspects of the Verbenaceae:
The bark of Avicennia alba is utilised for tanning. Some plants are cultivated as ornamentals, e.g. Callicarpa, Caroypteris, Clerodendrum, Petrea, Vitex, etc. The wood of Gmelina arborea is used for making drums, sitars, tom-toms and other musical instruments.
Lippia alba produces a valuable essential oil. L. citriodora (tropical America) yields ‘verbena oil’. The aromatic leaves of Premna tomentosa are employed as dinner plates and the wood for making combs. The tubers of Priva laevis (Argentina) are edible. The leaves of Stachytarpheta dichotoma are sometimes used as an alternate to tea.
Tectona grandis supplies a hard and durable timber which is good for ship building and other purposes. Vitex agnus-castus produces a valuable oil and V. celebica a fine timber. The leaves of V. negundo serve as a febrifuge; they are also used for preserving stored grains against insect attacks.
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