POLYGONACE^E. (BUCKWHEAT FAMILY.) 313 



ORDER 66. POL.YGOWACE.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 petaloid ; 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. Erlogronum. 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. R 11 in ex. Sepals 6, the outer spreading, the inner enlarging and appressed to the trian- 



gular akene. Stigmas 3, tufted. 



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



Styles 2 or 3 : stigmas capitate. 



1. ERIOGONUM, Michx. 



Involucre campanulate, 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 8-toothed 



or lobed : bracts foil aceous, rarely somewhat ternate. 



* Akenes membranous!?/ 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. Timbellatum, Ton. Tomentose: leaves glabrate above or gla- 

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

 reflexed : umbel simple, of 2 to 10 naked rat/s, 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-) 



