588 POLYGONACE. [Polygonum. 
spikes or racemes, often forming terminal panicles. Perianth 
inferior, persistent; segments 3-6, free or connate at the base, 
imbricate. Stamens 5-9, rar ely more or less, hypogynous or perigy- 
nous ; filaments capillary or subulate, free or connate at the base; 
anthers 2-celled. Ovary superior, compressed or 3-gonous ; styles 
1-3; ovule solitary, basal, orthotropous. Fruit a small hard inde- 
hiscent trigonous or compressed nut, usually enclosed in the per- 
sistent perianth. Seed erect, testa membranous; albumen copious, 
farinaceous ; embryo variable in position, radicle superior. 
A rather large order, spread over the whole world, but most abundant in the 
north temperate zone. Genera 30; species over 600. The roots of many species 
are nauseous and purgative, the medicinal rhubarb being a well-known instance. 
On the other hand, the stems and leaves are frequently acid and refreshing, as 
the garden- rhubarb and the common sorrel. Buckwheat (Fagopyrum) is the 
only edible plant of any consequence. Of the 3 New Zealand genera, Muehlen- 
beckia extends to Australia and South America; the remaining 2 are widely 
distributed in both hemispheres. 
Flowers hermaphrodite. Perianth-segments 5, not suc- 
culent in fruit 46 Be 5: .. 1. PoLyGonum. 
Flowers hermaphrodite. Perianth-segments 6, the 3 inner 
enlarging and closing over the fruit, not succulent .. 2. RUMEX. 
Flowers unisexual. Perianth-segments 5, enlarged and 
succulent in fruit .. ie a fs .. 3. MUEHLENBECKIA. 
1. POLYGONUM, Linn. 
Herbs, rarely shrubby at the base. Leaves alternate; stipules 
membranous, usually tubular and closely sheathing the stem. 
Flowers small, hermaphrodite, clustered; clusters either axillary 
or in racemes or spikes or panicles; bracts and bracteoles mem- 
branous, ochreate; pedicels usually jcinted. Perianth 5-partite, 
green or coloured ; segments equal or the 2 or 3 outer ones the 
largest. Stamens 5-8. Ovary compressed or 3-gonous; styles 2 
or 8, free or connate at the base; stigmas usually capitellate. 
Nuts compressed or 3-gonous, included in the persistent peri- 
anth. Seed albuminous; embryo excentric or lateral; radicle long, 
superior. 
A large and almost cosmopolitan genus, including over 150 species. The 
three found in New Zealand are all widely distributed. 
* Stems prostrate. Flowers in axillary clusters. 
Stems long, wiry, sparingly branched. Perianth 4 in. long. 
Nut minutely striate or punctate - . 1. P. aviculare. 
Stems short, compactly branched. Perianth hi in. long. 
Nut smooth and polished .. ‘ .. 2. P. plebeium. 
** Stems erect or ascending above. Flowers in slender terminal spikes. 
Leaves 2-5in., lanceolate. Stipules ciliate and pilose. 
Spikes very slender, 1-2 in. long oe sc .. 3. P. serrulatum. 
For references to several introduced species of Polygonwm, see the list of 
naturalised plants appended to this work. 
