POLYGONACE.E. (BUCKWHEAT FAMILY.) 313 



ORDER 66. POL.YGONACE^E. (BUCKWHEAT FAMILY.) 



Herbs, with alternate and entire leaves, or sometimes verticillate, and 

 stipules in the form of sheaths above the swollen joints of the stem or 

 none; flowers mostly perfect, with a more or less persistent calyx, a 

 1 -celled ovary bearing 2 or 3 styles or stigmas, and a single erect seed ; 

 stamens mostly 4 to 9. Flowers rather small, the perianth of 3 to 6 

 segments, the inner ones or all usually petatoid ; fruit an akene. 



* Flowers involucrate : stamens 9 : styles 3, with capitate stigmas : herbs or woody at base, 



with alternate or verticillate leaves, without stipules. 



1. Eriogonum. Involucre several-flowered, with 4 to 8 pointless teeth. Flowers ex- 



serted. Akene mostly 3-angled. Annuals or perennials. 



2. Oxytheca. Involucre few-flowered, herbaceous, with 3 to 5 straight acute or usually 



awned lobes. Flowers on exserted pedicels. Akene lenticular. Bracts ternate. 

 Annuals. 



* * Flowers without involucre : stamens 4 to 8 : styles 2 or 3 : herbs with alternate leaves 



and scarious sheathing stipules ; juice usually acid, acrid or pungent. 



3. Oxyria. Sepals 4, the outer smaller and spreading. Stigmas 2, tufted. Akene orbicu- 



lar-winged. Leaves reniform. 



4. liumcx. Sepals 6, the outer spreading, the inner enlarging and appressed to the trian- 



gular akene. Stigmas 3, tufted. 



5. Polygonnm. Sepals 4 to 6, equal, appressed to the triangular or lenticular akene. 



Styles 2 or 3 : stigmas capitate. 



1. EBIOGO3STUM, Michx. 



Involucre campannlate, turbinate or oblong. Perianth 6-parted, colored, 

 enclosing the akene. Herbaceous or somewhat woody, with radical or alter- 

 nate or verticillate leaves. 



1 . Involucres more or less broadly turbinate, not nerved or angled, 4 to S-toothed 

 or lobed : bracts foliaceous, rarely somewhat ternate. 



* Akenes membranously winged. 



1- E. alatum, Torr. Loosely silky-villous throughout, or the leaves 

 nearly glabrous except on the margin and midrib : leaves alternate, long, ob- 

 lanceolate : involucres pedunculate, solitary, with 5 erect teeth : flowers a line 

 long, yellow, nearly glabrous, abrupt at base : akene winged the whole length. 

 From Arizona and Texas to Nebraska. 



* * Akenes not winged. 

 -- Flowers glabrous. 



2. E. umbellatum, Torr. Tomentose : leaves glabrate above or gla- 

 brous, oblanceolate or spatnlate : involucres deeply lobed ; lobes becoming 

 reflexed : umbel simple, of 2 to 10 naked rays, on naked (rarely l-bracted) pedun- 

 cles. From Colorado to Oregon and California. 



Var. monocephalum, Torr. & Gray. A reduced dwarf alpine form, 

 the naked or bracteate peduncle bearing a solitary involucre : leaves small. 



3. E. heracleoides, Nutt. Similar, but the peduncle usually verticillate- 

 bracted: leaves narrower, mostly somewhat revolute or undulate: umbel 6- (1-11-) 



