Scrophulariaceae - Figwort Family

Common Toadflax (Linaria vulgaris)

Common Toadflax (Yellow Toadflax, 'Butter and Eggs') is also known as the wild snapdragon due to its resemblance to the snapdragon familiar in gardens which opens and closes like a pair of jaws when gently squeezed from the sides. (the upper and lower petals are said to be personate). This mechanism is to ensure some selectivity in choice of pollinator. potential pollinating insects land on the lower lip or palate and only insects heavy enough to depress the palate enough to open the floral tube can gain access to the pollen and nectar.

Though originally classed in the family Scrophulariaceae, molecular analysis suggests that Snapdragons and Toadflaxes are members of the Plantaginaceae, based on genetic similarity.

Linaria vulgaris. Note the nectar which is visible in the spurs.

The Scrophulariaceae includes some well-known and attractive plants, such as speedwells (Veronica), Foxglove (Digitalis purpurea), Toadflax (Linaria) and snapdragons (Antirrhinum, now included in the family Plantaginaceae or plantain family on the basis of DNA analysis but here we are going to use the more traditional field taxonomy as this is more familiar and still widely used). Similarly, Veronica now belongs to Plantaginaceae.

Linaria vulgaris is perennial with a creeping rootstock which gives out one or more stems from its nodes. The stems may be branched or simple (unbranched). The stalkless (sessile) elliptical or strapshaped leaves are in irregular whorls of 3. The flowers grow in dense racemes (raceme: an inflorescence with stalked flowers borne on a central axis). Two orange hairy ridges (palate) form a channel (of about 1 mm diameter) to guide the proboscis of the visiting insect. Only insects with long enough proboscises will ordinarily be able to reach the nectar, in this case certain bees. The bee also needs sufficient strength to prize apart the opening to the corolla (petal tube). Whilst feeding, the back of the bee may deposit any pollen on the stigma and collect any pollen from the anthers.

The copious quantities of nectar that can be seen in Linaria vulgaris have made it prone to nectar robbery. According to one study, short-tongued bees will steel the nectar without pollinating the plant, by biting a hole in the corolla, whilst long-tongued bees behave as genuine pollinators (Stout, J.C., J.A. Allen and D. Goulson, 2000. Nectar robbing, forager efficiency and seed set: Bumblebees foraging on the self incompatible plant Linaria vulgaris (Scrophulariaceae). Acta Oecologica 21: 277?283). This study found that 96% of open flowers (in southern England, UK) suffered nectar robbery! These flowers are self- incompatible and so cannot self-pollinate. However, despite the high incidence of nectar robbery, seed set remained high as genuine pollinators were sufficiently abundant.

The fruit capsule consists of two connected cells, each opening by 3 valves forming an apical pore with the seeds borne on the partition wall. Each plant produces an average of 30 000 seeds, of which about half are viable. Each seed is surrounded by a broad wing, however, experiments suggest that wind dispersal is of limited importance, as most seeds fall close to the parent plant.

Above: a seed of Linaria vulgaris. The black-brown seeds are up to about 2 mm in diameter with a very thin and extensive wing which is slightly concave on one surface, convex on the other (concave surface shown here) and notched on one side.

This plant occurs in hedges, field borders and on waste ground. It is native to Europe and some northern parts of Asia and is invasive in America, South Africa and East Asia. A form occurs called 'Peloria' which has a regular corolla bearing 5 spurs and intermediates with 3 spurs are also known. The variety latifolia has larger flowers and a slightly curved spur and more leaf-like bracts and reaches 120 cm in height (compared to 30 to 60 cm for the typical variety) but produces abortive fruit.

Above: Ivy-leaved Toadflax Linaria cymbalaria (Cymbalaria muralis). A more recent taxonomy places this genus in the Plantain family (Plantaginaceae). Unlike the Common Toadflax, the Ivy-leaved Toadflax is self-compatible and frequently self-pollinates. The prominent palette has two yellow spots. This species is a trailing perennial (with many procumbent stems) found in northwest Europe, USA including Alaska and Greenland. Branches root at the base. It frequently occurs on old walls (hence 'muralis'). The roundish reniform or heart-shaped (cordate) leaves are borne on long pedicels. The globular fruit capsule has two cells, each opening by three valves.

Above and below: Linaria maroccana (Moroccan Toadflax).

Below: Linaria purpurea (Purple Toadflax)

The next plant genus we shall examine has remained with the Scrophulariaceae: Verbascum (Mulleins).

Verbascum thapsus (Great Mullein)

Native to Europe and parts of Asia (see: http://powo.science.kew.org/taxon/770183-1). great Mullein occurs on dry banks, waste land, roadsides and hedge-banks, especially on calcareous, sandy and gravelly soils. The stem is stout and usually unbranched and up to 120 cm (4 feet) tall. The radical leaves are up to 35 cm or more in length and narrow to a short stalk. All but the lowest stem leaves are strongly decurrent (extending back down the stem where they attach) and diminish in size towards the apex. The stem is topped by the inflorescence (as are any branches if present) which is up to 30 cm (1 foot) tall and is described as a raceme or spike (flowers born on a central axis) with very short flower stalks (the absence of flower stalks gives us a spike, their presence a raceme so in this case it is a bit ambiguous but is actually a spikelike raceme of densely packed flowers). The bracts are longer than the sepals. This specimen was growing along the dry and stable part of dune by a salt marsh.

The flowers each have 5 sepals, 5 petals and 5 stamens. The 3 upper stamens have filaments clothed in woolly hairs and transverse anthers, whilst the 2 lower stamens have longer hairless filaments and differently shaped anthers. The corolla (petals) consist of a very short tube and a concave limb.

The leaves are very felty to the feel due to numerous hairs with stellate tips, similar hairs also occur on the calyx (sepals) and fruit capsules. The leaf blade gives rise to a wing which descends the stem to the previous leaf.

The capsule is about the size of a large pea and opens via two valves. It contains numerous small black conical seeds.

Veronica (Speedwells)

Article last updated:

28 March 2015
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