POLYGONIFLORJ:. 361 



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

 brush-like (indicated in Fig. 354 B). llliciim and Polygonumaxe insect-pollinated 

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

 of the stamens (d, in Fig. 35-1 C, and n in Fig. 356) ; a few small-flowered 

 Polygomim species are self-pollinated ; Buckwheat (P. fagopyrnm) is dimorphic 

 and has long-styled and short-styled flowers (Fig. S56). 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 (O.ryriu, Klmigiu). Trees and shrubs are found in the Tropics: 

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

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

 species, I\. undulatum and r Impolitic urn, are used in veterinary medicine. The 

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

 acetosn (Sorrel), 11. patient ia, R. scntattts, and Hheiiin itnditlatuut (petioles). 

 Several species of Pulyyoniun (P. Injdropiper and others) have a sharp, pungent 

 tastp. "Buckwheat " is the mealy fruit of Pulygonum fagopyrum (Central Asia) 

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

 ornamental plant. Calligouum in sandy and stony deserts. 



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

 short-ityleil ; a the anthers ; s( 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 (Peperomid) or intrapetiolar and cap- 

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

 the group Pipere<.e (Piper, Fig. 357, and Peperomin) are borne in 

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

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

 without bracteoles; generally stamens 3+3, and gynceceum 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, orthotropons ovule. Fruit a berry or drupe. Both 

 endosperm and perixperm are present, the latter being especially 

 well developed (Fig. 359). 



Piper ; generally shrubs with scattered leaves, and terminal 



