THE BUCKWHEAT FAMILV. 



55 



Of the sub-genus Persicaria the last 

 described species and the one which 

 follows illustrate its peculiarities. 



P. l\rsicaria, lady's thumb, a little 

 plant from Europe, has now become 

 well naturalised in this country and in 

 low grounds occurs prolifically as a weed. Its small deep 

 pink or purple flowers are packed closely in solitary, or 

 panicled spikes, while the alternate and linear-lanceolate 

 leaves are nearly sessile. At their bases are cylindric 

 ochrea:^ which are bristly. Another point of distinction 

 is the broadly ovoid, or at times triangular, achenes. 



P. avicuIart\Vv\oX.%X'A^^, or door-weed, occurs through 

 both cultivated and waste ground as a very common weed 

 and may be looked upon as a type of the sub-genus, 

 Aviculart\ which bears its flowers in axillary inflores- 

 icences. They are small with greenish calyxes, faintly 

 u tipped with pink. There are numerous small, linear- 

 oblong or oblanceolate leaves which at the bases of their 

 very short petioles appear to be somewhat jointed to 

 .the oblique ochreae. While the plant has prostrate, or 

 often ascending, branched stems, it is not one that ever 

 Lady's Thumb. assumes a twining habit. 

 P. sagittatiun, arrow-leaved tear-thumb, represents as does the next 

 species that sub-genus of the polygonums Echinocaulon, the members of 

 which climb over other plants by means of the small, recurved prickles 

 which arm the angles of their slender stems and petioles. The small, deep 

 pink flowers of this species grow thickly in rounded, terminal clusters 

 and the achenes they later produce are three-angled. At the bases of their 

 petioles the lanceolate-sagittate leaves have entire and oblique ochreas, 



P. arifbliiiDi, halberd-leaved tear-thumb, extends hardly further southward 

 than South Carolina. Its flowers are greenish or deep pink and the achenes 

 are lenticular. Its notably large and hastate leaves have at the bases of 

 their long petioles ochreas fringed at their summits and bristly about their 

 lower parts. 



P. duinentbriim, copse or hedge buckwheat, serves well as a type of the 

 section, Tiniaria which includes those polygonums with a twining habit of 

 growth. Often the branched stem of this species is very long. Its leaves 

 are ovate, deeply heart-shaped, or approaching hastate at the base while the 

 ochres are quite smooth. From axillary racemes the flowers nod and are 

 for the most part a greenish yellow. As well as in the south the plant 



