In this article we will discuss about:- 1. General Features of the Scrophulariaceae 2. Floral Range in the Scrophulariaceae 3. Divisions 4. Position and Affinity 5. Number and Distribution 6. Commonly Occurring Plants 7. Economic Aspects.
General Features of the Scrophulariaceae:
Habit – Herbs or shrubs, with collateral vascular bundles.
Leaves – Opposite or whorled, exstipulate.
Inflorescence – Cymose or racemose.
Flowers – Bisexual, irregular, hypogynous.
Calyx – Sepals 5, united, persistent.
Corolla – Petals 5, united, sometimes personate, often spurred.
Androecium – Stamens 4, epipetalous, didynamous or 2; disc annular or unilateral.
Gynoecium – Carpels 2, syncarpous, medianly placed; ovary superior 2-locular; ovules many in each loculus; placentation axile; style simple or bilobed.
Fruit – Capsule.
Seeds – Embryo slightly curved or straight; endosperm fleshy.
Floral Range in the Scrophulariaceae:
The flowers are provided with bracts and bracteoles. They are usually medianly zygomorphic, although regular flowers are seen in Scoparia and Verbascum.
The calyx is usually pentamerous, but the suppression of the posterior sepal takes place in Euphrasia and many species of Veronica. In Calceolaria, the two anterior sepals are entirely connate.
The corolla shows a considerable variation in its form. It is large and campanulate, as in Digitalis purpurea. In Scrophularia, it is small and suberect. It is four-lobed in Gratiola and other genera. It is furnished with spreading limbs in Veronica, the tube being almost absent. The lateral anterior petals may be spurred, as in Diascia.
The corolla can also form a pair of closed lips, e.g. Antirrhinum and Linaria.
All the five stamens are fertile and equal, as in Verbascum. In Russelia and others, the stamens are 4 in number with the reduction of the posterior stamen. In some cases, the anterior pair of stamens becomes longer than the posterior pair. Only 2 stamens are found in Veronica and other genera.
The carpels are generally 2 and equal, but the anterior carpel becomes large in Antirrhinum.
Divisions of the Scrophulariaceae:
The Scrophulariaceae is divided into two groups, one with two subfamilies and the other with a single subfamily:
Group A:
Posterior lobes of carpels cover two lateral lobes.
Subfamily I. Antirrhinioideae:
Leaves opposite, at least lower ones. Stamens 4. Examples- Antirrhinum, Calceolaria, Gratiola, Torenia, etc.
Subfamily. II. Pseudosolanioideae:
Leaves alternate. Stamens 5. Example- Verbascum.
Group B:
Posterior lobes of carpels not covering lateral lobes.
Subfamily I. Rhinanthoideae:
Stamens 4 or 2. Examples- Digitalis, Rhinanthus, Veronica, etc.
Position and Affinity of the Scrophulariaceae:
The Scrophulariaceae was treated by Bessey as an advanced member of his Scrophulariales, probably arising from the Bignoniaceae. Hallier regarded the Scrophulariaceae to be one of the primitive components of the Tubiflorae, incorporating into it such related families as the Globulariaceae, Lentibulariaceae, Plantaginaceae and Selaginaceae.
In Engler’s arrangement, the family appeared under the suborder Solanineae of the Tubiflorae. It was the opinion of Bentham-Hooker that the family belonged to the Personales which was placed between the Polemoniales and Lamiales. Hutchinson included the family in the Personales after the Solanales and before the Polemoniales.
The Scrophulariaceae agrees with the Solanaceae in general and with the tribe Salpiglossideae in particular in floral structure, but is separated by the collateral vascular bundles, nonplicate zygomorphic corolla, reduction of posterior stamens and medianly placed carpels.
It is allied to the Gesneriaceae and Orobanchaceae, but distinguished from them by the bilocular ovary. It bears an affinity with the Pedaliaceae and Bignoniaceae, but is set apart by the presence of endosperm in seeds. It is related to the Acanthaceae and Labiatae, but differs from them by the alternate leaves, absence of bracts and the characters of the corolla, ovary and fruit.
Number and Distribution of the Scrophulariaceae:
The Scrophulariaceae is compounded of about 220 genera and 3,000 species. The members of this family attain the peak of their development in the temperate zones of the world. However, they decrease in number as one approaches the tropical regions.
Commonly Occurring Plants of the Scrophulariaceae:
Snapdragon (Antirrhinum majus L.), Russelia equisetiformis Schlecht. & Cham., Torenia fournieri Linden ex Fourn. and Verbascum celosioides Benth. are garden plants.
Bacopa monnieri (L.) Pennel, Dopatrium junceum (Roxb.) Buch.-Ham. ex Benth., Limnophila indica (L.) Druce, Lindernia ciliata (Colsm.) Pennell, L.crustacea (L.) F.v. Muell and Verbascum chinensis (L.) Santapau are weeds.
Toad-flax [Kickxia ramosissima (Wall.) Janch.] is a prostrate herb, having sagittate leaves and yellow flowers.
Limnophila heterophylla Benth. is an aquatic plant, bearing submerged dissected leaves.
Lindenbergia indica (L.) Vatke is a herb with yellow flowers, growing on window sills and old brick walls.
Mazus pumilus (Burm. f.) Steen. is an annual herb, having tufted radical leaves.
Mecardonia dianthera (Swartz) Pennell is an erect herb with square stems, ovate-crenate leaves and white or whitish-yellow flowers.
Scoparia dulcis L. is a rigid perennial herb with nearly regular flowers whose corolla throat is densely bearded.
Striga densiflora Benth., a herb, is parasitic on the roots of Sorghums.
Economic Aspects of the Scrophulariaceae:
Economically, the members of the Scrophulariaceae are of limited value. The plants that are cultivated for showy flowers include Antirrhinum, Calceolaria, Collinia, Hebe, Kickxia, Mimulus, Pentastemon, Russelia, Veronica, Wulfensia, etc. Bacopa monniera is of medicinal importance for its nervine properties. Curanga felterrae is used as a febrifuge.
The leaves of Digitalis purpurea yield the drug ‘digitalin’, a powerful stimulant for the heart. The species of Euphrasia were formerly utilised as a source of eye wash; the European species of Scrophularia were once reputed to cure scrofula.
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