DESCRIPTIONS OF SOME COMMON WEEDS 179 



two, occasionally three, falling when the flower expands ; 

 petals four to twelve, spre*ading, soon falling; stamens in- 

 serted under the pistils, distinct, pistils one, many ovuled, 

 chiefly one-celled; fruit a capsule containing numerous 

 oily seeds. Genera 24 to 26, species about 200. Widely 

 distributed chiefly in the North Temperate Zone. The 

 opium poppy (Papaver somniferum) is sometimes weedy, 

 especially in old gardens. The smooth-pointed corn pop- 

 py of Europe (P. dubium) is found 

 in similar places. The celandine 

 (Chelidonium majus), with yellow 

 flowers, a yellowish juice, is some- 

 times a troublesome weed. 



Mustard Family (Cruciferae). 

 Herbs or rarely woody plants with 

 acrid, watery juice ; alternate leaves 

 without stipules; flowers in race- 

 mose or corymbose clusters, cruci- 

 form, of four deciduous sepals, and 

 four petals, placed opposite each 

 other in pairs, spreading and form- 

 ing a cross ; stamens six, two 

 shorter, one pistil, consisting of 

 two united carpels ; fruit a pod 

 either much longer than broad (a 



silique) or short (silicic) or inde- Fi s- "3- Crowfoot (Ra- 

 , . ,.., * nunculus sceleratus). 



hiscent, separating into joints ; seed 



without endosperm ; seed coat frequently mucilaginous ; 

 embryo large. 



About 1,500 species of wide distribution. The cabbage 

 (Brassica oleracea), native of Europe, has long been culti- 

 vated. 



Penny cress or French Weed (Thlaspi arvense, L.). 

 A smooth annual, six inches to one foot high, simple or 

 branched, root leaves petioled, stem leaves oblong or 

 lanceolate, sparingly toothed, the upper clasping; flowers 



