306 



EXPERIMENT STATION BULLETIN. 



BUCKWHEAT FAMILY. POLYGONACEAE. 



Mostly herbs with entire leaves and stipules in the form of sheaths extending around the stem; 

 flowers with a calyx more or less persistent; ovary one-celled, becoming an achene in fruit, flat- 

 tened or 3-4- angled. Among its 800 species the family contains few of economic importance, but 

 is rather conspicuous for the weeds it affords. Here are sorrels, docks, knotweeds, smartweeds and 

 others. 



Fig. 31 (31). 



Knot-grass. Door-weed. Polygonum 



aviculare L. A slender, prostrate or erect 

 annual (perennial farther south), dull or bluish 

 green in color, usually less than 30 cm. high; 

 leaves small; flowers small, inconspicuous; fruit 

 a triangular achene, dull, minutely granular 

 and striate. Common along paths and about 

 door yards. Native to this country, Europe 

 and Asia. 



Fig. 32 (32). 



Wild Buckwheat. Black Bindweed. 



Polygonum Convolvulus L. An annual, twin- 

 ing" or trailing vine, 10-90 cm. or more long; 

 leaves heart-shaped or halberd-shaped, pointed; 

 flowers greenish in slender, interrupted racemes; 

 fruit three-angled, dull, black; in cultivated 

 annual crops. Introduced from Europe. 



