62 



WEEDS. 



The "common penny cress, or smooth mithridate mus- 

 tard/' or the "Thlaspi arvense/' has the pouch orbicular, 

 compressed, entire at the base. Leaves oblong, toothed, 

 smooth. It is annual, and flowers in June and July. The 

 root is small and tapering. The whole plant is smooth, 

 about a foot high, branched ; the stem leafy, angular up- 

 wards. Leaves two or three inches long, clasping the stem 

 with their arrow-shaped base, their edges wavy and toothed. 

 Flowers numerous, small, white. Pouch large, erect, almost 

 perfectly orbicular. Seeds numerous. The warm pungent 

 taste of the plant is combined with a disagreeable garhck 

 flavour. 



The root being annual, it only remains to guard against 

 the perfecting of the seeds, by frequent cutting ofl* the growing 

 stems by the scythe. 



26. The " Goose-tansy, silverweed, or feathered cinque- 

 foil," or the " Potentilla" of botany, is a very common 

 weed in pastures recently laid down from the arable state. 

 The plant belongs to the class and order " Icosandria Poly- 

 gynia" of Linneus, and the natural order " Rosacese" of 

 Jussieu. 



Generic characters. — Calyx : perianth one-leaved, flattish, 

 ten-cleft ; the alternate segments smaller, reflex. Corolla : 

 petals five, roundish, spreading, inserted by their claws into 

 the calyx. Stamina : filaments twenty, awl-shaped, shorter 

 than the corolla, inserted into the calyx ; anthers elongate, 

 lunulate. Pistil : germens numerous, very small, collected 

 into a head ; styles filiform, the length of the stamens, 

 inserted into the side of the germ; stigmas obtuse. Peri- 

 carp none. Common receptacle of the seeds roundish, 

 juiceless, very small, permanent, covered with seeds, inclosed 

 within the calyx. Seeds numerous, acuminate, wrinkled. 



Essential character. — Calyx ten-cleft ; petals five ; seeds 

 roundish, naked, fastened to a small juiceless receptacle. 



The common species, or the " Potentilla anserina," has 

 the leaves interruptedly pinnate, serrate, silky underneath ; 

 stem creeping ; peduncles one-flowered. Root fibrous, and 

 penetrating deep. Stems creeping, round, jointed, reddish, 

 downy. Leaves, silvery, white underneath. Petals yellow, 



