402 POLYGONACEAE 



in heads, peduncled umbels, or solitary along the branches (either sessile or on 

 ''pedicels"), or terminal on scape-like stems. Calyx 6-parted or -cleft, colored, 

 persistent about the achene. Stamens 9, inserted on the base of the calyx. 

 Styles 3 ; stigmas minute, capitate. Achene triangular, except in a few species. 

 Embryo straight, in the axis of scanty endosperm; cotyledons foliaceous. 

 About 140 North American species, mostly western. (Greek erion, wool, and 

 gonu, knee or joint, the nodes hairy in some species.) 



The species of Eriogonum often show considerable variability. Favorable or unfavorable 

 conditions react most strikingly on the stems, branches and involucres, and least on the leaves 

 which are very constant in texture, outline and size. The leaves in the herbaceous species are 

 usually in a basal rosette, but even when typically so leaves may occasionally develop freely 

 at the nodes, as in E. virgatum, gracile, vimineum and dasyanthemum. Vigorous individuals 

 often develop many stems from the base (E. vimineum, caninum, and truncatum), or when 

 less vigorous branch only at first node or sparingly. The size and degree of branching of the 

 inflorescence is characteristically variable, particularly in the E. umbellatum and E. nudum 

 groups. Simple and compound umbels are often borne on the same individual, and umbels are 

 often condensed to a capitate condition or indeed reduced to a single involucre. Inflated stems 

 may be expected in any form of the E. inflatum and E. nudum allies. Where there are several 

 stems from the base, inflated and non-inflated stems may sometimes be borne in the same 

 rosette, as in E. inflatum and in E. trichopodum. The shape of the flower is important, but 

 inasmuch as in many species the flower changes in shape between anthesis and fruiting, invari- 

 able features in this regard should be guardedly separated from such characters as are subject 

 to modification as growth proceeds. For example, in E. incanum the short stipe-like base of 

 the flower in its early condition is abruptly expanded into a bowl-shaped upper portion; later 

 the calyx becomes vase-shaped and twice or thrice as long. In E. thomasii the calyx segments 

 are nearly plane in early anthesis, in fruit they are twice as large and conspicuously saccate. 

 In certain species some of the flowers in an involucre, especially the more shortly pedicelled 

 ones, are sometimes found to be staminate, a condition also met with occasionally in species 

 of Chorizanthe and Oxytheca. According to Miss S. C. Stokes, hybrids are quite common in 

 some of the groups. In Eriogonum fasciculatum the glandular area at base of the calyx which 

 provides the honey flow harvested by the domestic bee is very distinct. A similar area exists 

 in E. nudum but is far less developed. Both species are protandrous. Honey areas appear to 

 be absent from the calices of E. vimineum and its allies. 



A. Calyx not stipe-like at base. 



Involucres turbinate or campanulate, 4 or 5-toothed or lobed, not angled, always borne on 

 scattered pedicels, never congested in heads; annuals (except nos. 9 and 10); mostly 

 deserts or arid plains. Subgenus GANYSMA. 

 Plants with leaves at the nodes in the axils of the bracts as well as in a basal rosette, 



involucres 4-lobed or -toothed. 

 Involucres not cottony. 



Inner and outer calyx-lobes very unlike 1. E. angulosum. 



Inner and outer calyx-lobes nearly alike 2. E. gracillimum. 



Involucres conspicuously cottony 3. E. gossypinum. 



Plants with the leaves all in a basal rosette (except nos. 4 and 8), rarely in the axils of 

 the lower bracts; inflorescence with small bracts at the nodes, the bracts in 3s, 

 triangular or oblong, and often more or less connate at base. 

 Involucre 4-lobed or -toothed, few (usually 1 to 3) -flowered. 



Calyx nearly glabrous 4. E. spergulinum. 



Calyx at least in fruit with hooked bristles. 



Involucres 2-flowered ; achene exserted 5. E. hirtiflorum. 



Involucres 4 to 6-fl owered ; achene not exserted 6. E. inerme. 



Calyx hairy or glandular-hispid, its hairs not hooked. 



Calyx segments notched or 3-toothed at apex 7. E. apiculatum. 



Calyx segments entire. 



Leaves tomentulose or glabrate 8. E. ordii. 



Leaves hairy pubescent. 



Calyx pinkish 9. E. parishii. 



Calyx yellow 10. E. trichopodum. 



Inrolucre 5-lobed or -toothed, several-flowered. 

 Calyx hairy or pubescent. 



Stems usually inflated; leaves hairy-pubescent 11. E. inflatum. 



Stems not inflated or rarely. 



