ILLUSTRATED FLORA 



VOL. II 



Family 35. POLYGONACEAE. 



Buckwheat Family. 



Herbs, shrubs, or rarely vines or trees, with jointed stems. Leaves alternate, 

 opposite or whorled, often only basal, simple and generally entire. Stipules when 

 present united and sheathing. Flowers mostly perfect, on jointed pedicels. Calyx 

 2-6-parted or -cleft, the sepals or segments persistent, often petaloid. Petals none. 

 Stamens 2-9, inserted near the base of the calyx. Pistil solitary, free from the calyx ; 

 ovary superior, 1-celled ; ovule solitary, orthotropous, erect or pendulous ; styles 2-3 

 or rarely 4, distinct or partly united. Fruit a lenticular, 3- or rarely 4-angled achene, 

 usually invested by the persistent calyx. Embryo straight within the endosperm or 

 curved around it. 



A family of about 30 genera and 850 species, of wide geographic range. 



Leaves without stipules, basal, stem leaves when present opposite or alternate. (Eriogoneae.) 



Flowers subtended by one or several distinct bracts, or sometimes without bracts, never enclosed in an 

 involucre. 

 Bracts none. 2. Gilmania. 



Bracts present. 



Bracts 2-lobed, 2-saccate on the back, enlarged in fruit. 1. Pterostegia. 



Bracts not saccate or enlarged in fruit. 



Bracts floccose-tomentose; flowers in small head-like clusters. 



Calyx glabrous; stamens 3. 3. Nemacaulis. 



Calyx tomentose; stamens 9. 4. Hollisteria. 



Bracts glabrous; stamens 3. 5. Lastarriaea. 



Flowers enclosed in a turbinate or cylindric involucre. 

 Involucral teeth or lobes spine-tipped. 



Involucre mostly 4-5-toothed and the tube generally cylindric or prismatic, commonly 1 -flowered; 

 teeth often with uncinate spines. 6. Chorizanthe. 



Involucre mostly 4-5-lobed, the tube turbinate, never cylindric; teeth never uncinate; flowers several. 



7. Oxytheca. 



Involucral lobes or teeth not spine-tipped. 8. Eriogonum. 



Leaves with sheathing often scarious stipules, alternate; involucres none. 



Calyx 4- or 6-parted or urceolate and 6-lobed, at least in the pistillate flowers. (Rumiceae.) 



Calyx urceolate, becoming indurate and bur-like in fruit; outer lobes spinescent. 9. Emex. 



Calyx 4- or 6-parted, the inner cycle erect, the outer reflexed and smaller; flowers perfect or unisexual. 



Sepals 6; leaves not reniform. 10. Rumex. 



Sepals 4; leaves reniform. 11. Oxyria. 



Calyx S-parted, equal, often petaloid and erect in fruit; stigma capitate. (Polygoneae.) 12. Polygonum. 



1. PTEROSTEGIA Fisch. & Mey. Ind. Sem. Hort. Petrop. 2: 48. 1835. 



Annuals with weak slender dichotomously branched stems and opposite entire or 2-lobed 

 leaves. Involucre axillary, solitary with a single 2-lobed bract, becoming enlarged, scarious 

 and reticulate in fruit. Flowers solitary, sessile, exceeding the involucre. Calyx 6- or 

 rarely 5-parted. Stamens 3 or 6, inserted at the base of the sepals. Achenes loosely enclosed 

 by the involucres, triangular, glabrous; cotyledons rounded, acumbent. [Greek, meaning 

 wing and covering, referring to the involucral bract.] 



A monotypic genus of western North America. 



1. Pterostegia drymaroides Fisch. & Mey. Pterostegia. Fig. 1300. 



Pterostegia drymarioides Fisch. & Mey. Ind. Sem. Hort. Petrop. 2: 48. 1835. 

 Pterostegia diphylla Nutt. Journ. Acad. Phila. II. 1: 168. 1847. 

 Pterostegia diphylla var. biloba Nutt. loc. cit. 

 Pterostegia microphylla Nutt. loc. cit. 



Stems very slender, decumbent or prostrate, branching from the base, 1-5 dm. long, usually 

 with elongated internodes, thinly hirsute. Lower leaves fan-shaped, 3-15 mm. broad, usually 2- 

 lobed and the lobes often crenately toothed or shallowly lobed, narrowed at base to the petiole, 



