666 



POLYGONACEAE. 



VOL. I. 



i. Persicaria amphibia (L.) S. F. Gray. 



Water Persicaria. Willow-weed. 



Fig. 1630. 



Polygonum amphibium L. Sp. PI. 361. 1753. 

 Persicaria amphibia S. F. Gray, Nat. Am. Brit. PI. 2 : 



268. 1821. 

 Polygonum Harturightii A. Gray, Proc. Am. Acad. 



8 : 294. 1870. 



Aquatic, perennial, glabrous or pubescent; 

 stem floating or submersed, simple or sparingly 

 branched, 4-2o long. Leaves oblong, elliptic 

 or elliptic-lanceolate or narrowly lanceolate, l$'- 

 4' long, petioled, obtuse or subacute at the apex, 

 slightly inequilateral, rounded or narrowed at the 

 base, sometimes ciliate; ocreae cylindric, those 

 of the branches often longer than the internodes, 

 their limbs sometimes spreading, usually gla- 

 brous; raceme terminal, usually solitary, i'-i' 

 long, dense, erect, oblong or ovoid ; calyx rose- 

 color, 5-parted ; stamens 5, exserted; style 2-cleft, 

 exserted; achene orbicular-oblong, i-J" long, bi- 

 convex, black, smooth and shining, or granular. 



In ponds and lakes, Quebec to Alaska, New Jersey, 

 Kentucky, Colorado and California. Europe. As- 

 cends to 2000 ft. in the Adirondacks. Ground-willow. 

 Willow-grass. Red shanks. Heartsease. July-Aug. 

 Several species, reducible to this and the following, have been described by Dr. E. L. Greene 

 (Leaflets i : 26-45). 



2. Persicaria Muhlenbergii (S. Wats.) 

 Small. Swamp Persicaria. Fig. 1631. 



Polygonum amphibium var. emersum Michx. Fl. Bor. 



Am. i : 240. 1803. 



P. Muhlenbergii S. Wats. Proc. Am. Ac. 14: 295. 1879. 

 P. emersum Britton, Trans. N. Y. Acad. Sci. 8 : 73. 1889. 

 Persicaria Muhlenbergii Small ; Rydb. Fl. Colo. 1 1 1. 1906. 



Perennial by long creeping or horizontal root- 

 stocks, glabrous or strigose-pubescent ; stem erect or 

 assurgent, commonly simple, channeled, enlarged at 

 the nodes, i-3 high. Leaves ovate-lanceolate or 

 oblong-lanceolate, or the upper sometimes narrowly 

 lanceolate, 2'-8' long, acute or usually acuminate 

 at the apex, rounded or cordate at the base, petioled, 

 the lateral nerves prominent, sometimes forking; 

 ocreae cylindric, becoming loose, not ciliate ; racemes 

 i or 2, erect, i'-3' long, linear-oblong, dense; calyx 

 dark rose-color, 5-parted ; stamens 5, exserted ; style 

 2-cleft, exserted; achene broadly obovate or orbicu- 

 lar, \\" long, very convex, lenticular, black and 

 slightly granular, but shining. 



In swamps and moist soil, Ontario to British Colum- 

 bia, Virginia, Louisiana and Mexico. July-Sept. 



3. Persicaria lapathifolia (L.) S. F. Gray. 

 Dock-leaved or Pale Persicaria. Fig. 1632. 



Polygonum lapathifolium L. Sp. PI. 360. 1753. 

 P. incarnatum Ell. Bot. S. C. & Ga. I : 456. 1817. 

 P. lapathifolia S. F. Gray, Nat. Arr. Brit. PI. 2: 270. 1821. 

 P. lapathifolium incanum Koch, Syn. Fl. Germ. 711. 1837. 

 P. lapathifolium nodosum Small, Mem. Torr. Club 5: 140. 

 1894. 



Annual, stem simple or much branched, erect or as- 

 cending, swollen at the nodes, i-3 high, the peduncles 

 and pedicels often glandular. Leaves lanceolate or ob- 

 long-lanceolate, 2'-io' long, usually broader than those 

 of the preceding, attenuate to the apex, acuminate at the 

 base, short-petioled, ciliate, glabrous or pale-pubescent, 

 inconspicuously punctate ; ocreae cylindric, ribbed or 

 striate; racemes panicled, i'-4' long, drooping, narrow, 

 rather dense ; calyx pink, greenish or white, 5-parted ; 

 stamens 6; achene broadly oblong or ovoid, lenticular, 

 i" long, brownish or black, slightly reticulated but shin- 

 ing, its faces concave. 



