THE BUCKWHEAT FAMILY, POLYGONACE&. 



The Buckwheat family contains several weedy plants, some of which 

 are troublesome on farms. The objectionable members of the family all 

 belong to two genera, the Docks (Rumex), and the Smartweeds, or Knotweeds 

 (Polygonum). Many of these require some attention to keep them under 

 control, but none can be said to be very difficult to eradicate on well-kept 

 farms. The Docks are tall-stemmed perennial weeds with tap-roots, found in 

 pastures and meadows ; they live for many years but, with few exceptions, 

 as in the case of the Sheep Sorrel, do not spread from the root. The achenes 

 enclosing the seeds are shaped like those of the buckwheat, being triangular 

 in cross section, or as the name buckwheat (which is merely a corruption 

 of beechwheat) indicates, shaped like small beechnuts. There is no 

 true corolla, the achenes being surrounded merely by the 6-parted calyx, 

 3 segments of which are small and the other 3 large, wing-like and 

 variously shaped and veined in the different species. One or all three of 

 these wings may bear a seed-like-corky tubercle on the outside. The "seeds" 

 of all species are much alike, and the wing-like segments, often found at- 

 tached to the seeds as they occur among crop seeds, are a great help in recog- 

 nizing the different species. 



The weeds of the Knotweed and Smartweed division of the family are 

 found in three rather distinct groups of the genus Polygonum : 



(1) The Knotweeds are well represented by the very common DOORWEED, 

 Polygonum, aviculare, L., which accompanies civilized man everywhere, and 



is found along roads and trails, forming mats of spreading wiry jointed 

 stems with a leaf, a pair of silvery scales and a small cluster of flowers at 



each joint, each flower producing a slender reddish-brown triangular achene 



, i l f of an inch long. 



(2) The Smartweeds, or Persicaries, are represented by several plants of 

 various habits, some are perennials with extensive running rootstocks, as the 

 SWAMP PERSICARY, Polygonum Muhlenbergii, Wat., which is sometimes 

 very persistent in low undrained spots, others are fleshy-stemmed annuals, 

 as the LADY'S-THTTMB, Polygonum Persicaria,' L., the shining black, T V 

 of an inch, ovate heart-shaped, hollowed out on one side or roundly triangular 

 seeds (achenes) of which [Plate 54, fig. 37 natural size and enlarged 8 times] 

 are frequently found among the seeds of grasses and clover, and the DOCK- 

 LEAVED PERSICARY, Polygonum lapathifolium, L., a common tall-growing 

 and rather aggressive weed among grain and clover on rich low land in all 

 parts of Eastern Canada. The "seeds" of the latter, which also occur with 

 the above, are T V of an inch long, more roundly heart-shaped, chocolate 

 brown, hollowed on both faces and never triangular. A larger (^ inch) 

 blackish "seed" closely resembling both of the preceding, but more fre- 

 quently bearing the spike-like base of the pistil at the tip, is that of the 

 (.TLANDTTLAR PERSICARY, Polygonum pennsylvanicum, L. The "seeds" of 

 this plant, as those of the Lady's-thumb, are sometimes triangular. 



(3) The third group contains plants mostly with twining or climbing 

 stems and with arrow-head-shaped leaves, as the Wild Buckwheat [Plate 43]. 



82 



