BRITISH WILD FLOWERS. 
43 
THE HORSE-RADISH. (C. Armoracia, Lin.) 
This well-known plant is supposed to be not a true native; though it has been found growing wild in 
England for centuries. It, however, rarely flowers, and still more rarely perfects its seeds; though no plant can 
be more readily propagated by the root. It is, indeed, extremely difficult to clear the ground of it when it has 
been once planted, as it will continue coming up in various places, wherever the smallest portion of the root has 
been left in the soil. 
III.—THE PENNY-CRESS TRIBE. 
Seed-pod a silicle ; partition very narrow ; valves keeled-shaped. Seeds oval, sometimes bordered. 
GENUS XII. 
THE PENNY-CRESS. (Thlaspi, Lin.) 
Lin. Syst. TETRAD YN AM IA SILICULOSA. 
Generic Character.— Silicula emarginate; valves navicular, winged at the back; cells two or many-seeded. Petals equal. Calyx 
equal at base. (Dec.) 
Description, &c. —This is a genus entirely composed of weeds with inconspicuous white flowers. They are 
only found in the Northern Hemisphere, and are not very abundant anywhere. The name of Thlaspi is said to 
be derived from a Greek word, signifying to flatten, in allusion to the shape of its seed vessels. 
1. —THE MITHRIDATE MUSTARD. (Thlaspi arvense, Lin.) 
Engravings. —Eng. Bot., t. 1659 ; 2nd ed., t. 897 ; and our jig. I Specific Character. —Silicula orbicular, nearly flat, shorter than 
3, in PI. 10. I its stalk. Leaves smooth, oblong, toothed. Stem erect. (Smith.) 
Description, &c. —This plant is more ornamental in the seed-pod than in the flower, and, indeed, it is 
generally in the former state that it is met with, as the flowers remain on a very short time, while the seed-pods 
are of very long duration. The seed-pods are, indeed, very curiously formed; the pod itself resembling two 
boats fixed together, with their keels projecting, and being furnished with a large wing on each side. The plant 
is an annual, and grows generally by the road-side, or on old walls, or in unfrequented streets; but it is much 
less common now than it was formerly. The seeds are very sharp and pungent in their taste, and they were 
frequently used as a substitute for mustard by country people a century ago. They were also firmly believed to 
be an antidote against poison ; and hence the name of Mithridate Mustard, from the old fable of its being 
impossible to poison Mithridates, from his skill in making antidotes. The plant possessing no beauty, it has 
never been cultivated in gardens. 
2 .—THE COMMON PENNY-CRESS. (Thlaspi perfoliatum, Lin.) 
Engravings. —Eng. Bot., t. 2354 ; 2nd ed., t. 898. heart-shaped, rather sharp at the base, clasping the branched stem. 
Specific Character. —Silicula inversely heart-shaped. Stem-leaves Style very short. (Smith.) 
Description, &c. —The perfoliate leaves of this species readily distinguish it from the Mithridate Mustard. 
The seed vessels are also much smaller and less ornamental. It is only found in limestone districts, and it 
generally grows in stone-pits. It is an annual, flowering in April and May, about six weeks earlier than the 
preceding species. 
o 2 
