POLYGONUM 
125 
16. POLYGONUM AVICULARE. Common Knotgrass. Plates 132, 133, 134 
Polygonum mas vulgare Gerard Herb. 451 (1597); Ray Syn. ed. 3, 146 (1724); P. mas minus Gerard loc. 
cit . ; P. oblongo angusto folio Ray loc. cit. ; partim. 
Polygonum aviculare L. Sp. PI. 362 (1753) partim ; Boreau FI. Centr. France ii, 559 (1857) including 
P. agrestinum, P. polychnemiforme, P. denudatum , P. humifusum p. 560, partim; Syme Eng. Bot. viii, 63 (1868) 
partim; Rouy FI. France xii, in (1910) partim; P. heterophyllum Lindman in Svensk Bot. Tidskrift vi, 690 
(1912). 
Annual. Stem — central one erect when young, much branched ; branches long (up to 6 dm.), 
decumbent, lower internodes often about 3 — 5 cm. long. Ochreae more or less scarious above, 
lacerate at maturity, brown at the base, more or less silvery at the top. Petioles shorter than 
the ochreae. Laminae heterophyllous, broadly elliptical to sublinear ; larger ones on the main 
branches up to 4 — 5 cm. long, subtending the smaller branches, more or less caducous ; smaller 
ones on the axillary branches, about half the size or less, often rather minute at the apices 
of the branches, occasionally caducous. Inflorescences few-flowered to 1 -flowered. Pedicels short. 
Flowers , early July to October. Perianth polysepalous or almost so, usually pink with a white 
margin. Stamens usually 8. Achenes trigonous, ovate to subelliptical, 2 — 3 mm. long and about 
half as broad ; the sides channelled or almost smooth, concave, the broadest side usually symmetrical, 
projecting a little from the persistent perianth or enclosed by it, chestnut or dark brown in colour, 
rarely almost black. 
Professor C. Lindman, of Stockholm, has recently elucidated the forms of knotgrasses (in Svensk Bot. Tidskrift , vi, 
673 — 696 (1912)). We have here adopted his arrangement, but with a few modifications. For example, we retain the 
Linnaean name P. aviculare for Lindman’s P. heterophyllum : we retain Jordan’s P. rurivaguin (which Lindman reduces 
to a subspecies) as a species ; and we refer two of Lindman’s varieties to the putative hybrid P. aviculare x aequale. 
Lindman’s treatment of the group is the only one which we have found to be of any real value. The only account 
with which it may be reasonably compared is that by Boreau (Ft. Centr. France ii, pp. 559 — 560 (1857)); but Boreau 
subdivides the group into too many species whose distinguishing characters are, in several cases, unsatisfactory. 
(a) P. aviculare var. vulgare Desvaux Observ. PI. Angers 98 (1818); P. aviculare Boreau loc. cit., including 
P. agrestinum , P. denudatum, et P. humifusum ; P. aviculare Norman in Trans. Tyneside Nat. Field Club v, 
142 (1863)!, inch P. agrestinum\ ; P. avicidare f. agrestinum Syme Eng. Bot. viii, 64 (1868) including f. vulgatum 
p. 65; P. heterophylhim Lindman excl. vars. !. 
leones : — Smith Eng. Bot. t. 1252, as P. avicidare ; Curtis FI. Lond. i, 76, as P. aviculare ; Martin FI. Rust., 
t. 91, as P. aviculare ; FI. Dan. t. 803, as P. avicidare ; Beck in Reichenbach Icon. t. 207, as P. aviculare. 
Camb. Brit. FI. ii. Plate 132. (a) Flowering branches, (b) Flowers (both enlarged). ( c ) Persistent 
perianth, enclosing ripening achene (enlarged"!. (d) Achene (enlarged). Huntingdon (E. W. H.). 
Exsiccata : — Billot, 73, as P. aviculare ; Reichenbach, 925, as P. aviculare var. erectum. 
Branches commonly 5 or 6 dm. long. Laminae — the larger ones up to 4—5 cm. long and 
half as broad. Achene about 3 mm. long, included or nearly so. 
Arable land, road-sides, and waste places, northwards to Zetland. 
Europe. 
( b ) P. aviculare var. angustissimum Meisner in DC. Prodr. xiv, 98 (1856); P . heterophyllum var. angustis- 
simum Lindman op. cit. p. 691 !. 
leones : — Camb. Brit. FI. ii. Plate 133. (a) Flowering branches. ( b ) Portion of fruiting branch, with 
stipular sheath, persistent perianth, and achene (enlarged), (c) Achene (enlarged). Huntingdonshire (E. W. H.). 
Exsiccata : — Herb. FI. Ingric. iv, 547, as P. aviculare var. angustifolium. 
Stem and branches rather slender. Ochreae up to 13 mm. long, rather silvery towards the top. 
Laminae linear-lanceolate, much narrower than in the preceding varieties. 
On river-gravel, near Huntingdon ; and doubtless elsewhere. 
Europe. 
( c ) P. aviculare var. litorale Koch Syn. 618 (1837); P. aviculare race litorale Rouy FI. France xii, 113 
(1910); P. heterophyllum var. litorale Lindman op. cit., p. 691 (1912)!. 
leones : — Beck in Reichenbach Icon. t. 208, fig. 3 — 4. 
Camb. Brit. FI. ii. Plate 134.. ( a ) Flowering branches. (b) Lower part of stem. ( c ) Fruits and 
persistent perianth (one enlarged), (d) Flowers (one enlarged), (e) Achenes (one enlarged). (/) Portion of 
stem with ochrea (enlarged). Isle of Wight (E. W. H.). 
