WEEDS OF THE Bl'CK WHEAT FAMILY. 



67 



22. Polygonum aviculabe L. 

 X. 1.) 



Knot-grass. Door-weed. Goose-grass. (A. 



Stem prostrate or sub- 

 erect, slender, dull bluish- 

 green, 4-18 inches long; 

 leaves oblong or linear, 

 ^-J inch long, nearly ses- 

 sile. Flowers axillary, in 

 clusters of 1-5, small 

 short-stemmed, greenish 

 with white or pink bor- 

 ders ; stamens 5-8. Seeds 

 dull black. 1/10 inch long. 

 3-angled and minutely 

 granular. (Fig. 34.) 



Very common, form- 

 ing mats of spreading, 

 wiry, jointed stems in 

 yards and along path- 

 ways and roadsides 

 where the ground is 

 much trodden; also in 

 cultivated lands. June- 

 Nov. This is one of the 

 social weeds, such as plantain, burdock, catnip, etc., which accom- 

 panied the white man in his march across and conquest of the 

 North American Continent. Holmes refers to it in the lines: 



"Knot-grass, plantain — all the social weeds. 

 Man's mute companions, following where he leads." 



An infusion of it was formerly supposed to retard bodily growth 

 and is referred to by Shakespeare in the lines: 



Fig. 34. Showing the flower and fruit. (After Small.) 



"Get you gone, you dwarf ; 

 You minimus, of hindering 



knot-grass made." 



The civet knot-grass (P. erectum L.) is also often found with 

 the common form. Tt is erect or ascending, 1-2 feet high and has 

 the leaves and often the flowers yellowish, the former 1-2 inches 

 long. Both species are attacked by a mildew and sometimes by a 

 smut. 



Remedies: pulling or mowing before the seeds ripen; thorough 

 cultivation with hoed crops; cement and concrete walks for yards. 



