POLYGONUM ARI FOLIUM. 



HALBERD-LEAVED TEAR-THUMB. 



NATURAL ORDER, rOLVGONACE.1£. 



Polygon u^r arifolium, Linnxus. — Stem grooved-angled ; leaves halberd-shaped, taper- 

 pointed, long-petioled ; flowers somewhat racemed (few); peduncles glandular-bristly; 

 calyx often four-parted ; stamens six; styles two, very short ; achenium lenticular (large). 

 (Gray's Manual of tlie Botany of the Northern United Slates. See also Chapman's Flora 

 of the Southern United States, and Wood's Class-Book of Botatiy.) 



HE natural order to which our present species belongs 

 comprises only few genera, but its representatives are 

 nevertheless to be found over the greater part of the world. 

 The Dock, the Sorrel, the Buckwheat, and the Rhubarb are 

 among its more northern species, while another member of the 

 order, the Seaside Grape, well known for its beautiful berries, is 

 at home in Florida and still farther towards the tropics, beyond 

 the southern boundaries of our territory. The order is named 

 Polygonaccct, from the genus Polygonum, to which the subject 

 of this chapter belongs. Polygonum is the largest genus in the 

 order, numbering more than two hundred species ; but these 

 latter are so variable and so difificult to define, that much differ- 

 ence of opinion exists among botanists as to their identification. 

 In consequence of this difference of opinion, many attempts 

 have been made to divide the species into several genera, but 

 as these attempts were not universally recognized as legitimate, 

 their chief result has been to originate quite a number of 

 synonyms, such as Persicaria, Bistorta, Avicitlaria, Towara, 

 and others, most of which are now used as convenient sub- 

 sectional names. Some of our best botanists, however, are still 



