280 LEGUMINOSAE (PEA FAMILY) 



15. Trifolium Fendleri Greene, Pitt. 3: 221. 1897. Low glabrous peren- 

 nial, 8-20 cm. high, usually branched from the base: leaflets from obcordate 

 to obovate-oblong, or sometimes oblong-lanceolate, minutely serrulate: 

 heads slender-pedunculate; involucre many-lobed, somewhat lacerate: flowers 

 from nearly white to rose-purple: calyx-tube 10-nerved, half as long as the 

 slender teeth: pod turgid, stipitate, 2-seeded. T. involucratum. Colorado to 

 New Mexico. 



16. Trifplium Wonnsjoldii Lehm. Ind. Sem. Hort. Hamb. 17. 1829. 

 Annual, biennial, or even seemingly perennial by slender rootstocks in some 

 localities: stems simple or sparingly branched, erect or decumbent, 1-4 dm. 

 long: leaflets obovate-oblong, obtuse, pectinate-denticulate, 2-3 cm. long: 

 heads hemispherical, 15-25 mm. in diameter; the involucre broad, laciniate- 

 aristate: calyx-tube scarious, 10-nerved, much exceeded by the linear lobes: 

 standard emarginate, purple. T. involucratum and T. pauciflorum in part; 

 the former of these is Mexican and the latter is of the range to the northwest 

 of ours. Our species seems to extend from California (where it is perennial) 

 into Colorado. 



8. ROBINIA L. LOCUST 



Trees or shrubs, often with prickly spines for stipules. Flowers showy, in 

 hanging axillary racemes. Base of the leafstalks covering the buds of the 

 next year. Calyx slightly 2-lipped. Standard large and rounded, turned 

 back. Pod 2-valved, flat and thin, margined on one edge. 



1. Robinia neo-mexicana Gray, Mem. Am. Acad. N. S. 5: 314. 1855. 

 Shrub 1-2 m. high: stipular prickles sub recurved, sharp and stout; leaflets 

 elliptical or oblong: peduncles and the short crowded racemes hispid with 

 straight glanduliferous hairs: calyx finely hispid: corolla rose-color: pods 

 glandular-hispid. Southern Colorado and southward. 



9. ASTRAGALUS L.* VETCH 



Chiefly herbs (ours perennials), with odd pinnate leaves and spiked or 

 racemed flowers. Calyx 5-toothed. Corolla usually long and narrow; stand- 

 ard narrow, equaling or exceeding the wings and blunt keel, its sides reflexed 

 or spreading. Stamens diadelphous. Pod several-many-seeded, various, 

 mostly turgid, one or both sutures usually projecting into the cell, either 

 slightly or so as to divide the cavity lengthwise into two. Mature pods are 

 usually necessary for certainty in determination of those species with which 

 one is not familiar through long association. 



Pods 2-celled, the septum perfect SERIES I. 



Pods 1-celled, but the cell divided by an incomplete septum formed by the 

 intrusion of the ventral or the dorsal suture, or by both being more or 

 less intruded. (In Phaca septum sometimes wholly wanting.) . . SERIES II. 



Pods 1-celled, no intrusion of either suture SERIES III. 



* This large and difficult genus is richly represented in the Rocky Mountains. The fol- 

 lowing are the principal attempts to elaborate the North American species: Torrey and 

 Gray, Fl. N. A. 1: 328-353; Gray, Proc. Am. Acad. 6: 188. 1866; Watson, King's Report, 

 435. 1871; E. P. Sheldon, Geol. and Nat. Hist. Surv. Minn. 1: 116-176. 1894. Recently 

 Rydberg has given us a very helpful outline and key to the Colorado species (Bull. Torr. Bot. 

 Club 32: 657. 1905), arranging them under seventeen genera. To each of the foregoing 

 scholarly elaborations grateful acknowledgment is made. In the following treatment of the 

 genus the aim has been merely to facilitate the recognition of species, and therefore the 

 keys are largely artificial and the species not necessarily in the sequence of true relation- 

 ship. In the interest of simplicity for the one who wishes to know plants by their names 

 (if for no other reason), it has seemed wise not to follow the recent tendency to segregate 

 a popularly recognizable genus. The name Astragalus will "be retained for the whole rather 

 than replaced by a considerable series of names representing groups that shade into each 

 other so gradually that even with a list of their technical characters before one, there is 

 often doubt as to the disposition to be made of some particular specimen. The proposed 

 names, however, are very useful in the designation of sections, and Rydberg 's service in 

 indicating the boundaries of these and in enumerating the species under each is a valuable 

 one. His paper has been heavily drawn upon for the present treatment of the genus. His 

 generic names are given and the main grouping shown. 



