178 



WEEDS AND USEFUL PLANTS. 



Obs. Tms worthless weed occurs in most cultivated grounds, — and is 

 usually very abundant among the stubble, after a crop of wheat : but, 

 if the laud be good, the plant seems te be smothered or choked out, the 

 next season, by the crop of clover and timothy. It is always ready, 

 however — like several other coarse weeds — to make its appearance 

 whenever the grassy turf is broken up. The curious anomaly above 

 mentioned, — of the flowers on the terminal spikes being all pistillate, — 

 is frequently met with. 



9. XAN'THIUM, Tournef. Clot-bur. 



[Greek, J^anthos, yellow ; a color said to be produced by the plant.] 



Heads monoecious, in spicate clusters — the sterile spikes at the summit. 



Fig. 119. Flowering summit of tbe Cockle-bur (Xanthium strumarium) , with heads of 

 staminate flowers above, the pistillate ones below. 120. A separate staminate flower very 

 much enlarged. 121. A head of (2) pistillate flowers enclosed in the prickly involucre. 



