DICOTYLEDONES. 63 
Genus CLXXIV.—POLYGONUM (Linn.) 
356. P. ConvoLvuLus (Linn.), Black Bindweed. 
Searce. 7 
Nether Scapa; fields in Harray (Prof. Trail) ; farm 
of Quoyer, Birsay (Sept. 1905, M. Spence). 
357. P. AVICULARE (Linn.), Knot-grass. Common. 
(a) AGRESTINUM (Jord.) 
(b) VULGATUM (Syme). 
(c) MICROSPERMUM (Jord.) 
(d) LITORALE (Link.) 
(a) (b) and (ce) are given in Dr Fortescue’s list ; 
(d) is a form sometimes met with on the sandy shore. 
358. P. PERsIcARIA (Linn.), Spotted Kvnot-grass. 
Fairly common. 
In wet patches in many fields on the Mainland, 
at least; Harray and Birsay (Prof. J. W. H. Trail). 
359. P. LAPATHIFOLIUM (Linn.), Pale Knot-grass. 
Scarce. 
Skail, Westray (Dr Flett); Swanbister—intro- 
duced (Dr Boswell). 
360. P. AMpHIBIUM (Linn.), Amphibious Bistort. 
Fairly common. 
Var. aquaticum. In several places—Birsay, North 
Ronaldshay ; Loch of Housby, Birsay, &e. 
Var. terrestre. In several places—Deerness, Birsay, 
&e.; Crantit (July 1876); Loch of Brue, Lady, Sanday 
(July 1883, Col. H. H. Johnston, C.B.); Bridge of 
Brodgar ; Skail (Dr Boswell). 
