Polygonum. | LXIII. POLYGONACEX, 385 
from P. aviculare by its thicker stems, larger and thicker, more glaucous 
leaves, larger scarious stipules, brown and much veined at the base, 
larger flowers, and especially by the nuts, often 2 lines long, project- 
ing beyond the perianth, and very smooth and shining. Older speci- 
- mens, grown in drier sands, have a woody, perennial stock, with short, 
thick branches, completely covered by the stipules, the internodes being 
-all very short. 
‘In maritime sands, on most of the seacoasts of the northern hemi- 
sphere, and here and there also in the south. Common on the south 
coast of England and the Channel Islands. fl. end of summer and 
autumn. The P. Roberti, Loisel, or P. Raw, Bab., is rather a young or 
a luxuriant state of this plant than a distinct variety, although those 
names are sometimes given to the maritime variety of P. aviculare. 
3. P. Convolvulus, Linn. (fig. 871). Black Bindweed.—A glabrous 
annual, with a twining stem as in Convolvulus. Stipules short. Leaves 
stalked, heart-shaped or broadly sagittate, and pointed. Flowers in 
little loose clusters ; the lower ones axillary, the upper ones forming 
loose, irregular terminal racemes. Styles 3. Fruiting perianth not 2 
lines long; the 3 outer segments closely surrounding the triangular 
‘nut, and sometimes sharply keeled on the midrib, but rarely winged. 
In cultivated and waste place, throughout Europe, in central and 
Russian Asia, and North America, to the Arctic regions. Frequent in 
Britain. Fl. summer and autumn. [The var. pseudo-dumetorum, Wats., 
has broad wings on the outer sepals. | 
4. P. dumetorum, Linn. (fig. 872). Copse P.—Stem, foliage, and 
inflorescence of P. Convolvulus, of which it may be a mere variety ; but 
it is more luxuriant, and the 3 angles of the fruiting perianth are more 
or less expanded into a white, scarious wing, which is often decurrent 
on the pedicel, the whole perianth being often 3 lines long. The nut 
is also usually more shining. 
In hedges, open woods, or rich, cultivated places, in Europe, Russian 
Asia, and North America, but not so common, nor extending so far 
northward, as P. Convolvulus. In Britain, chiefly in the southern 
counties of England. fl. end of summer, and autumn. 
5. P. viviparum, Linn. (fig. 873). Vevrparous P.—Stock perennial 
and tuberous, with simple, erect, slender stems, 4 to 6 or rarely 8 inches 
high. Radical leaves on long stalks, narrow-oblong or linear ; stem- 
leaves few, nearly sessile or clasping the stem. Spike solitary and 
terminal, slender, 14 to 3 inches long. Flowers, when perfect, pale 
flesh-coloured, and small, with 3 styles, but the lower ones, and some- 
_ times all, are converted into little red bulbs, by which the plant 
propagates. 
In alpine pastures, often at great elevations, in all the great mountain- 
ranges of Europe and Asia, descending to lower levels in the north, and 
penetrating far into the Arctic regions. Frequent in the Highlands of 
Scotland, and occurs also in northern England and North Wales, and on 
Ben Bulben, in Ireland. Fl. summer. 
6. P. Bistorta, Linn. (fig. 874). Buistort, Snakeweed.—Perennial root- 
stock thick, and often spreading considerably. Radical leaves in broad 
patches, on long stalks, ovate-lanceolate or cordate, often 3 to 6 inches ~ 
long. Stems simple and erect, 1 to 2 feet high, with a few nearly sessile 
leaves, and terminating in a single, dense, oblong, or cylindrical flower- 
2B 
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