POLYGONACEAE 



5 2 9 



Polygonaceae (EP., BH.). Dicots. (Archichl. Polygonales; Curvem- 

 bryae BH.). 30 gen., 750 sp., chiefly N. temp.; a few trop., arctic, 

 and southern. Most are herbs whose 

 1. (exc. Eriogoneae) possess a peculiar 

 sheathing stipule or ochrea (ocrea) 

 clasping the stem above t .e leaf-base. 

 This forms a char, feature of the fam. 

 The infl. is primarily racemose, but 

 the partial infls. usu. cymose. [See 

 Eriogonum.] Fls. $, reg. , cyclic or 

 acyclic. The former have usu. the 

 formula P 3 + 3, homochlamydeous ; 

 A 3 + 3, G (3); but many vary from 

 this type. Oxyria is 2-merous ; others, 

 e.g. Eriogonum, Rheum, have branch- 

 ing of the outer sta. The acyclic fls. 

 have P 5, arranged according to the 

 2/5 phyllotaxy (e.g. Polygonum), A 

 5 8, G (3). Ovary i-loc. with i 

 erect orthotr. ov. and 3 styles. Fls. 

 pollinated by wind or by insects. Fr. 

 almost always a triangular nut, with 

 smooth exterior. The seed contains 

 an excentric curved or straight embryo surrounded by mealy endosp., 

 sometimes ruminate. The fruits are usually wind-distributed; the 

 persistent P usu. forms a membranous wing. Others are provided 

 with hooks. 



Classification and chief genera (after Dammer) : 

 A Flower cyclic, endosp. not ruminate. 

 I. RUMICOIDEAE. 



1. Eriogoneae (no ochrea) : Chorizanthe, Eriogonum. 



2. Rumiceae (ochreate) : Rumex, Rheum, Oxyria. 



Floral diagram ofPolygala mvr- 

 tifolia (after Eichler); the gland d 

 as in P. Chiimaebuxus. Petals 

 and bracts black; the missing petals 

 represented by^dotted lines, the 

 missing sta. by *. 



Floral diagrams (after Eichler). A, Rheum; B, Polygonum tataricum; C. 

 Rumex; D. Polygonum lapathifolium. Bracts and bracteoles are omitted, and in 

 C and D the axis also. Glands in B shaded. The asterisks represent missing sta. 



W. 



34 



