POLYGON1FLORJ3. 361 



POLLINATION. Rumex is wind-pollinated, the stigmas are therefore large and 

 bru-h-Hke (indicated in Fig. 354 B). Rheum and Polygonum are insect-pollinated 

 and have therefore capitate stigmas, etc.; honey-glands are situated at the base 

 of the stamens (d, in Fig. 354 C, and n in Fig. 356) ; a few small-flowered 

 Polygomi m -species are self-pollinated ; Buckwheat (P. fagopyrum) is dimorphic 

 and has long-styled and short-styled flowers (Fig. 556). Pol. bistorta is protan- 

 drous and homostyled. 



About 750 species, most of which are found in the temperate regions of the 

 Northern Hemisphere, some reaching as far as the snow line or into the Arctic 

 regions (Oxyria, Konigia). Trees and shrubs are found in the Tropics : 

 Coccoloba, Triplaris. Rheum is Central Asiatic. The thick rhizomes of R. 

 officinale (Rhubarb) are officinal. The rhizomes of the ordinarily cultivated 

 species, R. undulatum and rhaponticum, are used in veterinary medicine. The 

 following are cultivated as culinary plants for the sake of their leaves : Rumex 

 acetosa (Sorrel), R. patientia, R. scutatus, and Rheum undulatum (petioles). 

 Several species of Polygonum (P. hydropipef and others) have a sharp, pungent 

 taste. "Buckwheat " is the mealy fruit of Polygonum fagopyrum (Central Asia) 

 and is of value as a farinaceous food. P. cuspidatum (P. sieboldi, Japan) is an 

 ornamental plant. Calligojium in sandy and stony deserts. 



FIG. 356. Flower of Polygonum fagopyrum in longitudinal section: 1, long-styled ; 2, 

 short-styled ; a the anthers ; st the stigmas ; n nectary. 



Order 2. Piperaceae (Peppers). Shrubs or herbs, often 

 with nodose, jointed stem ; leaves simple, entire, often with curved 

 veins ; stipules wanting (Peperomia) or intrapetiolar and cap- 

 like, often enclosing the terminal buds (Piper). The flowers in 

 the group Piperece (Piper, Fig. 357, and Peperomia) are borne in 

 spikes with fleshy axes (club-Like), seldom in racemes, the outer 

 ones are crowded and are 5 or unisexual, always small, naked and 

 without bracteoles; generally stamens 3+3, and gynoaceum 3, but the 

 number of the stamens may be reduced by suppression to 2, and the carpels to 1. 

 The flowers are situated in the axils of the small, generally 

 shield-like floral-leaves. The ovary is always unilocular and has 

 one upright, orthotropous ovule. Fruit a berry or drupe. Both 

 endosperm and perisperm are present, the latter being especially 

 well developed (Fig. 359). 



Piper ; generally shrubs with scattered leaves, and terminal 



