CLASS VIH. ORDER II.] POIYGONUM. 577 



connect it with P. aviculare, on account of which circumstances we 

 have selected the name of dubium. 



1 1. P. mariti'mum. (Fig. 657.) Intermediate Knot-grass . Flowers 

 axillary ; leaves glaucous, elliptic-lanceolate, rough on the margins, 

 and rolled back ; stipules large, about twelve ribbed, bifid, at length 

 much divided; stem herbaceous, with numerous short joints, much 

 branched; fruit longer than the perianth, smooth and shining; root 

 annual. 



P. marinum, Raii. Syn. 147. (excluding all the synonyms.) 

 P aviculare. E. English Flora, vol. ii. p. 238. Hooker, British Flora, 

 vol. i. p. 185. 



Roots of long twisted fibrous branches, somewhat woody. Stems 

 with numerous long straggling procumbent branches, round, nume- 

 rously striated, glaucous, the joints numerous, about half an inch 

 apart, leafy to the end. Leaves elliptic-lanceolate, the margins rough, 

 and strongly rolled back, of a glaucous green, tapering at the base into 

 a footstalk, the under side rather paler than the upper, with a promi- 

 nent mid-rib and lateral veins, about an inch long, with an acute or 

 obtuse point. Stipules large, often half an inch long, tubular, cleft 

 into two oblong lanceolate segments, at length much divided, the base 

 a bright chesnnt brown, twelve ribbed, and often with intermediate 

 ones, prominent, and rather rough ; above it is pale, very thin, mem- 

 branous. Inflorescence axillary clusters, of about four flowers, each 

 elevated on a rather long slender simple stalk, green at the base, white 

 or pink on the margins. Perianth larger than either of the two above 

 species, cleft about half way down into five, rarely four, roundish or 

 ovate obtuse segments, each with a rather stout mid-rib. Stamens 

 scarcely half as long as the perianth. Filaments dilated in the lower 

 half into a lanceolate form, the upper half awl-sbaped. Anthers 

 roundish, flat, yellow. Styles very short, with small obtuse stigmas. 

 Fruit ovate-lanceolate, quite smooth and shining, of a chestnut brown 

 colour, acutely triangular, longer than the perianth, the point crowned 

 with the base of the styles, the base enveloped in the loose persistent 

 perianth. 



Habitat. Near the sea; Looe Bar, and other parts of the Cornish 

 coast, since the time of Ray. C. A. Johns, Esq. Sea shore, Isle of 

 Arran, and other places about the mouth of the Clyde, Sandymount, 

 and other places near Dublin. Mr. T. J. Mackay. 

 Annual ; flowering during the summer months. 



This species is essentially distinguished from either of the above 

 by its large twelve ribbed stipules, its revolute leaves, and its nume- 

 rous short jointed stems; but it is allied to P. dubium, by the size, 

 colour, and surface of the nuts. From P maritimum of Linn, it 

 differs in being an annual, not perennial, as is that species, which is 

 shrubby, and with larger stipules than those of our plant. 



