1911 Encyclopædia Britannica/Scrophulariaceae

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SCROPHULARIACEAE, in botany, a natural order of seed plants belonging to the sympetalous section of Dicotyledons, and a member of the series Tubiflorae. It is a cosmopolitan order containing about 180 genera with about 2000 species; the majority occur in temperate regions, the numbers diminishing rapidly towards the tropics and colder regions. About 30% of the species are annual herbs, such as eye bright (Euphrasia officinalis), cow-wheat (Melampyrum), and species of Veronica”

Fig. 1.—Foxglove (Digitalis purpurea).
1, Corolla cut open showing the
  four stamens, rather more
  than 1/2 nat. size.
   showing the thick axial
   placenta bearing numerous
   small seeds.
2, Unripe fruit cut lengthwise,  3, Ripe capsule split open.

more than 60% are biennial or generally perennial herbs and under shrubs, such as species of Veronica, mullein (Verbascum), foxglove (Digitalis; fig. 1), &c., while shrubs and trees are rare; Paulownia, a native of the mountains of Japan, a tree with large leaves and handsome panicles of violet flowers, is grown in European gardens.

The stem is sometimes prostrate and creeping, as in ivy-leaved toad-flax (Linaria Cymbalaria) and some of the native British Veronicas, but generally erect as in foxglove, figwort, mullein, &c.; a -few are climbers as Rhodochiton and Maurandia. The South African genera Hyobanche and Harveya are parasites almost devoid of chlorophyll with scale-like leaves; and many genera are semi parasitic, having green leaves, but attaching themselves by root-suckers to 'roots of grass, &c., from which they derive part of their nourishment; such are Euphrasia, Rhinanthus, Pedicularis, &c. A few genera are aquatic, e.g. Abulia (old world tropics), and have much divided submerged leaves and entire aerial leaves. The leaf-arrangement varies; the leaves are alternate as in Verbascum, or the lower leaves are opposite and the upper alternate as in Antirrhinum (snapdragon), or all are opposite (Mimulus), or whorled (some Veronicas). All varieties of leaf-arrangement are found in the one genus Veronica (q.v.), in some New Zealand species of which the leaves are small and oppressed to the stem. The flowers are solitary in the leaf-axils, as in Mimulus, species of Linaria, &c., or form spikes or racemes which are terminal as in foxglove, species of Veronica, &c., or axillary as in Veronica (Charnaedrys section). Cymose inflorescence's also occur, as in Verbascum, consisting of dichasia arranged in spikes, racemes or panicles. The flowers are hermaphrodite, hypogynous and zygomorphic in the median plane, being often more or less two-lipped, and having five sepals joined below and persisting in the fruiting stage five petals uniting to form a corolla of very various shape, generally four stamens, the fifth (posterior) being suppressed or represented by a rudiment, while the anterior pair are longer than the posterior, and two generally equal carpels in the median plane forming a two-celled ovary containing numerous anatropous ovules on a thick axile placenta, and bearing a simple or bilobed style (fig. 2).

Fig. 2a Fig. 2b Fig. 2c
Fig. 2.—Floral Diagrams of Scrophulariaceae.
a, Linaria. b, Veronica. c, Verbascum.

When a terminal flower is present it becomes regular as in toad-flax, where radial symmetry is produced by development of a spur to each petal—such flowers are termed peloric; all the flowers in a spike are sometimes peloric. In Euphrasia and many species of Veronica the posterior sepal is suppressed, and in Calceolaria the anterior petals are completely united. The form of the corolla shows great variety, depending on the length and breadth of the tube—which in Veronica is almost obsolete, while in foxglove it is large and almost bell-shaped—and the development of the limbs, which are spreading in Veronica, small and almost erect in figwort, or form a pair of closed lips as in Linaria and Antirrhinum. In Linaria the anterior petal is spurred; in Calceolaria a very short tube is succeeded by a two-lipped limb, a smaller upper lip representing the two posterior petals and a larger, often very large, lower lip representing the three anterior petals. In Verbascum the five segments are almost equal, forming a nearly regular corolla; in Veronica the two posterior petals have united and the corolla is four-lobed. The approach to regularity in the corolla in Verbascum is associated with the presence of five fertile stamens, but the three posterior are generally larger than the two anterior. In Veronica, Calceolaria and other genera only two stamens are present. The anthers generally open introrsely by a longitudinal slit; their form shows great variety. These differences in the form of the corolla, the position and length of the stamens and the form of the anthers, are associated with their pollination by insects which probe the flower for honey, which is secreted by a disk surrounding the base of the ovary or by special nectaries below it. Verbascum and Veronica with a short-tubed corolla represent an open type of flower with more exposed nectar; in foxglove the honey is at the base of the long tube, and a bee crawling to reach it will rub with its back the anthers or stigmas which are placed on the upper side of the bell. The closed flowers of Linaria and Antirrhinum can be visited only by insects which are strong enough to separate the lips. In Euphrasia and others the pollen is loose and powdery, and the anthers have appendages which when touched by the head of the insect-visitor cause the pollen to be scattered.

The fruit is generally a capsule surrounded at the base, or sometimes as in yellow-rattle (Rhinanthus) enveloped in the persistent calyx; it opens by two or four valves, or, as in Antirrhinum, by pores. Occasionally it is a berry. The seeds are generally small and numerous, rarely few and large as in Veronica. In Linaria Cymbalaria the fruit becomes buried by the stalks bending downwards when ripe.

The order is divided into tribes by characters derived from the number of fertile stamens present and the form of the corolla. It is well represented in Britain by 13 genera, viz. Verbascum (mullein), Linaria (toad-flax), Antirrhinum (snapdragon), Scrophularia (figwort), Limosella—a small creeping annual found on edges of ponds, Sibthorpia, a small herb with creeping thread-like stems, Digitalis (foxglove), Veronica (speedwell), Bartsia, Euphrasia (eyebright), Rhinanthus (yellow-rattle), Pedicularis (louse-wort) and Melampyrum (cow-wheat). An American species of Mimulus (M. Langsdorfi) has become naturalized by river-sides in many places. Several genera are well known in gardens; such are Calceolaria, an important genus in temperate South America, Collinsia, Pentstemon and Mimulus (musk), also American genera.

Scrophulariaceae are closely allied to Solanaceae (q.v.), from which they are distinguished by the median position of the carpels, and generally by the zygomorphic flower; Verbascum and its allies, in which the flower approaches regularity, form a connecting link. An anatomical distinction is found in the arrangement of the wood and bast in the stem, which is collateral, not bicollateral as in Solanaceae.