24 



WEEDS. 



most parts of Europe. Leaves arrow-shaped, lobes acute. 

 Flowers generally solitary ; bractes, minute, awl-shaped, re- 

 mote from the flower, Root perennial, creeping, striking 

 deeply into the ground, not easily extirpated. Stems numer- 

 ous, angular. Leaves alternate, petioled, smoothish. Flowers 

 flesh-coloured, sometimes white, sweet-scented, opening only 

 in clear weather ; peduncles axillary, generally one-flowered, 

 thickened above. The juice is slightly purgative, and the 

 blossoms give a deep orange or yellow tincture to water, 

 which is heightened by alum and alkahs. It flowers in June 

 and July. 



This weed is most common on dry gravelly soils, where it 

 wanders over whole fields, twining round the stalks of the 

 grain, and very much injuring the crop, especially when it 

 has been laid by heavy rains. The roots run deeply and very 

 widely. It brings plants to the ground, or checks their vege- 

 tation, by injuring their structure. Being perennial, it must 

 be rooted out by repeated ploughings done in dry weather, 

 and by carefully picking ofl* the roots and burning them. 

 The roots are very vivacious, and the smallest bit left in the 

 ground will spring and rise to the surface. 



18. " Knot-grass," or the '^Polygonum aviculare" of botany, 

 is not an uncommon weed on tillage lands. The plant be- 

 longs to the class and order " Octandria triginia " of Linneus, 

 and the natural order Polygonese" of Jussieu. 



Generic character. — Calyx: perianth inferior, of one-leaf? 

 turbinate, internally coloured, in five deep ovate, obtuse, per- 

 manent segments. Corolla none, unless the calyx be taken 

 for such. Stamina : filaments generally eight, awl-shaped, 

 very short ; anthers roundish, incumbent. Pistil : germen 

 superior, triangular ; styles mostly three, thread-shaped, very 

 short; stigmas simple. Pericarp none, the calyx folding- 

 over the seed. Seed one, acute, with three, rarely only two 

 angles. 



Efisential character. — Calyx: in five deep segments, 

 coloured, petal-like, permanent. Seed one, superior, angular, 

 covered by the calyx ; stamens and styles uncertain in 

 number. 



