POLYGONACEAE 181 



Over 600 species in various parts of the world, 

 comparatively few in S. A., among them Polygonum atra- 

 phaxoides with mostly 4-merous flowers. (Fig. 83, Nos. 3, 4.) 



Ecology. Flowers wind- or insect-pollinated. The 

 fruitlets are adapted in various ways to dispersal by wind, 

 water or animals by means of wings, spongy tissues and 

 hooks or spines. In most cases it is the persistent perianth 

 which becomes modified, sometimes the peduncle or the 

 axis of the inflorescence. 



Some species are cultivated on account of the farin- 

 aceous endosperm, viz. Fagopyrum esculentum (buckwheat), 

 from Eastern Asia, others for ornamental purposes, e.g. 

 Rheum Collinsianum and Rh. nobile\ or as vegetables 

 (rhubarb, the young leaf-stalks of several other species of 

 Rhemn). Rh. officinale and Rh. palmatum (China) yield 

 the drug known as rhubarb-root (the rhizome). 



Rumex Acetosella (sheep sorrel^ Steenbok-zuriny) and Emex 

 australis (Duiveltjes-doom) are troublesome weeds: the former 

 may be combated by liming the soil, the latter, like the 

 nearly allied E. spinosa^ only by weeding. (Flor. Cap. v, 1, 459.) 



SYNOPSIS OF GENERA. 



A. Perianth herbaceous, greenish, 6-fid, in 2 whorls of 3 each; stamens 6; 



stigmas penicillate. 



a. The 3 outer perianth-segments enlarging with the fruit, spiniferous 



at the apex and back. (Plate 47, E, page 191. Fig. 83.) 



1 S. A. species, E. australis. 1. Emex Neck. 



b. The 3 outer perianth-segments remaining small, the 3 inner 



segments enlarging, veiny, membranous, enclosing the fruit. 

 Over 100 species, 19 in S. A. (Dock, zariny). (Fig. 83.) 



2. Rumex L. 



B. Perianth coloured, 5-fid (1 spec. 4-fid) ; stamens 8; stigmas capitate. 



a. Perianth-segments free; fruit mostly compressed or 3-cornered, 



not winged. (Plate 47, A, page 191.) 



Over 150 species, 18 in S. A. 3. Polygonum L. 



b. Perianth-segments of fertile flower connate into a tube. Nuts 



mostly winged. 



7 species. E and No. 4. Oxygonum Burch. 



