200 PARIETARIA. 



{CLASS iv. ORDER i. 



1. P.officina'lis, Linn. (Fig. 25y.) common Pellitory-of-thc-Wall. 

 Leaves ovate-lanceolate, three-ribbed above the base; each leaf of 

 the involucrum with about seven segments, surrounding seven 

 flowers, the central one fertile. 



English Botany, t. 879. English Flora, vol. i. p. 222. Lindley, 

 Synopsis, p. 218. Hooker, British Flora, vol. i. p. 72. 



Root somewhat woody, with numerous downy fibres. Stem from 

 one to two feet high, erect, or procumbent at the base, angular, or 

 deeply furrowed, branched and leafy, reddish, and more or less thickly 

 clothed with soft pubescence. Leaves alternate, ovate-lanceolate, on 

 slender footstalks, three-ribbed above the base, dark-green and nearly 

 smooth above, paler and hairy beneath. Inflorescence small, axillary, 

 hairy clusters, arising from the base of the leaves. Involucrum formed 

 of two pieces, each cut into about seven ovate segments, containing 

 three apparently fertile flowers, but the central one has a pistil only, 

 while the lateral ones have both stamens and pistil ; and arising between 

 the two portions of the involucrum is a seventh fertile flower, with an 

 entire perianth which closely surrounds the pistil, and remains but 

 little altered as the plant advances to maturity, while the perianth of 

 the perfect flowers becomes much lengthened ; the stamens at first in- 

 curved, the anthers closely surrounding the pistil in the centre of the 

 flower; when the flower is completely expanded, the Jilaments, which 

 are remarkably jointed, have become highly elastic, but retain their 

 original curved position, until further progress of vegetation is made, 

 or some excitement is given to them by external causes ; the stamens 

 are suddenly thrown backwards by the elastic power of the filaments, 

 the shock at the same time bursting the anthers, and the pollen is pro- 

 fusely scattered around. This remarkable property in the filaments 

 may be best observed on a hot summer's day, and they are readily 

 excited into motion by agitation of the plant. Fruit small, ovate, 

 black and shining, closely invested by the calyx. 



Habitat. Walls, the crevices of rocks, and amongst rubbish ; fre- 

 quent. 



Perennial ; flowering during the summer months. 

 This plant was formerly in great repute as a diuretic : the expressed 

 juice was used externally as a fermentation, or sweetened with sugar, 

 and taken internally. It is without smell, and its taste is simply her- 

 baceous. In the practice of the present day, it is seldom or never used. 

 It is reported that this plant, laid in bunches, or scattered among corn 

 in granaries when infested with the corn-weevils, will either destroy or 

 drive away those destructive insects. It is said to contain so great a 

 proportion of nitre, that in making an extract from it, the mass has 

 been known to take lire. 



