20 WILD FLOWERS OF THE BRITISH ISLES 
pouched ; petals 4, entire, with long claws ; stamens 6, in pairs, one pair shorter than the other 
two ; carpels 2, the style so short as to appear absent, and the stigma slightly 2-lobed. Pod long, 
narrow, roundish or compressed, divided lengthwise into 2 cells by a thin partition, to 
either side of which the seeds are attached, the shell opening from base to apex by 2 valves 
(siliqua). Herbs with variously shaped leaves. 
Thale Cress. (Sisymbrium Thalianum, J. Gay.)— As just described. Flowers 
minute, | inch across, white; the pods narrow, slightly curved upwards; the stem 6-10 inches 
high, simple or with the upper part branched ; the root leaves in a rosette, oblong and toothed, 
and those of the stem narrower and stalkless (sessile). 
Common. Dry banks and walls. April — October. Annual. 
Common Hedge-mustard. (Sisymbrium officinale, Scop.)— Flowers minute, £ inch 
across, pale yellow [as described in the genus Hedge-mustard (Sisymbrium)], the pod being about 
\ inch long, narrow, hairy, tapering from the base to the point, and closely pressed to the 
main stem ; the stem 1-3 feet high, erect, the upper half with spreading branches ; the leaves 
deeply lobed to the midrib (pinnatifid), with the lobes turned downwards towards the base 
(runcinate), the terminal lobe being the largest. \J°/ate 13. 
Common. Waysides and waste places. June — July. Annual. 
Flixweed. (Sisymbrium Sophia, Linn.)— Flowers small, | inch across, pale yellow, the 
petals being shorter than the sepals, with long, narrow (linear), erect pods, forming long 
erect terminal clusters. [As described in the genus Hedge-mustard (Sisymbrium).] Stem 
1-3 feet high, erect, and the leaves deeply lobed to the midrib into narrow segments which are 
again, and sometimes again, divided in a similar fashion (bi- or tri-pinnatifid). 
Not common. Waysides, waste places. June — August. Annual. 
London Rocket. (Sisymbrium Irio, Linn.) — Flowers small, pale yellow, with the very 
long, slender, ascending pods overtopping the flowers. [As described in the genus Hedge- 
mustard (Sisymbrium).] The stem 1-2 feet high, erect, branched, and the leaves deeply lobed or 
divided into separate leaflets to the midrib (pinnatifid or pinnate). Called London Rocket 
because it sprang up in abundance on the ruins of London after the Great Fire of 1666. 
Very rare. Old walls and waste places. June — July. Annual. 
Garlic Mustard, Jack-by-the-Hedge, Sauce-alone. (Sisymbrium Alliaria, Scop.) 
— Flowers larger, £ inch across, pure white ; pods long, roundish, stiff, smooth. [As described in 
the genus Hedge-mustard (Sisymbrium).] The stem 1^-3 feet high, and the leaves stalked, 
broadly heart-shaped (cordate), and coarsely toothed. The whole plant is smooth, shining, 
of a fresh green in the early spring, and smells of garlic when gathered or bruised. [ Plate 13. 
Very common. Hedgerows, sides of streams, &c. April — June. Biennial. 
TREACLE-MUSTARD. (ERYSIMUM, LINN.) — Flowers usually yellow, in flattish clusters 
(corymbs) lengthening in fruit. Sepals 4, erect, sometimes with the 2 side ones pouched ; petals 4, 
narrow, with long claws ; stamens 6, in pairs, one pair shorter than the other two; carpels 2, with 
a very short or a longer style and a broad or 2-lobed stigma. Pod long, narrow, 4-sided, divided 
lengthwise into 2 cells by a thin partition, to either side of which the seeds are attached, the shell 
opening from base to apex by 2 valves (siliqua), the seeds being in 1 row in both cells. Hairy 
plants, with closely pressed hairs and entire toothed leaves. 
Common Treacle-mustard, Worm-seed Mustard. (Erysimum cheiranthoides, 
Linn.) — The only British species. As just described. The flowers small, [t inch across, 
pale yellow, with whitish sepals ; erect pods, f-i inch long ; the stem 6 inches to 3 feet high, erect, 
