PEA FAMILY 235 



the two lower petals are joined by tlieir edges to form the keel; the banner in the 

 bud enfolds the wings which in turn cover the keel-petals; all the claws are free 

 from one another. Petals essentially hypogynous, rarely perigynous in ours. Sta- 

 mens 10, united into a sheath around the ovary (monadelphous), or the upper 

 stamen distinct from the others (diadelphous), or sometimes all distinct. Pistil 1, 

 superior, 1-celled. Fruit a legume (2-valved pod), with 1 row of seeds on the 

 ventral side, commonly opening by both the dorsal and ventral sutures, the valves 

 twisting in opposite directions, or sometimes indehiscent. Seeds mostly kidney- 

 shaped, without endosperm. — Amorpha has but one petal. Acacia has numerous 

 stamens. Cytisus and Ulex (ours) have no stipules; their calyces are 2-lipped. 

 The seeds of Cassia have endosperm. The pod in Astragalus is sometimes 2-celled. 

 Calliandra has numerous stamens and a sympetalous corolla. — Genera about 490 

 and species about 11,000, all regions of the earth, especially in the tropics and on 

 plains and steppes of temperate lands. 



Bibliog. — Alefeld, TJeber Vicieen (Bonplandia 9:139-153, — 1861). Gray, A., Characters of 

 some new plants of California and Nevada [new species of Leguminosae] (Proc. Am. Acad. 

 6:522-527,-1865). Baillon, H., Leguminosae in Nat. Hist. Plants 2:20-382, figs. 15-208 (1872). 

 Taubert, P., Leguminosae (Engler & Prantl, Nat. Pflzfam. 3^:70-396, figs. 38-136,-1888). 

 Holzinger, J. M., Eange of Amorpha fruticosa (Erythea 1:131-132, — 1893). Eastwood, A., 

 Eediscovery of Thermopsis macrophylla (Zoe 5 : 76-78, — 1900) . Macbride, J. F., Notes on certain 

 Leguminosae of the tribe Psoraleae (Contrib. Gray Herb. 65:14-23, — 1922). Johnston, I. M., 

 Parkinsonia and Cercidium (Contrib. Gray Herb. 70:61-68,-1924). Eydberg, P. A., Fabaceae: 

 Psoraleae (N. Am. Fl. 24:1-64,-1919; 24:65-136,-1920). Britton, N. L., and Kose, J. N., 

 Caesalpiniaceae (N. Am. Fl. 23:201-340,-1930). 



Economic Eefs. — Holzinger, S. J., Mesquite (Forestry and Irrigation 8:447-453, 5 ill., — 

 1902). Hitchcock, A. S., Alfalfa growing (U. S. Dept. Agr. Farmers Bull. 215, pp. 1-39, figs. 

 1-7,-1905). Coe, H. S., Sweet Clover: growing the crop (U. S. Dept. Agr. Farmers Bull. 797:1- 

 34, figs. 1-11,-1917) ; utilization (I.e. 820:1-32, figs. 1-13,-1917). Piper, C. V., & McKee, E., 

 Bur Clover (U. S. Dept. Agr. Farmers Bull. 693:1-14, figs. 1-7,-1923). Beath, O. A., Poison- 

 ous Plants [Oxytropis, Astragalus, Lupinus] (Proc. Soc. Agr. Sci. 39:39-47,-1919). Pieters, 

 A. J., Sweet Clover (U. S. Dept. Agr., Lflt. 23:1-8, figs. 1-3,-1928). Cottle, Kathleen B., 

 Value of Melilotus indica to agriculture (Mo. Bull. Cal. Dept. Agr. 18:489-490,-1929). Brock, 

 A. A., Alhagi camelorum (Mo. Bull. Cal. Dept. Agr. 18:641-642,-1929). Braun, E. W., Alfalfa 

 (Univ. Cal. Agr. Exp. Sta. Bull. 521:1-37, figs. 1-11,-1931). Ball, W. S., and Bobbins, W. W., 

 Camel Thorn (Mo. Bull. Cal. Dept. Agr. 22 : 258-259, ill.,— 1933) . Bottel, A. E., Introduction and 

 control of Camel Thorn (Mo. Bull. Cal. Dept. Agr. 22:261-263, figs. 1-3,-1933). 



A. Corolla regular or only slightly irregular, not at all papilionaceous (obscurely so in no. 3) ; 

 stamens distinct (except in no. 1) ; trees or shrubs (herbs or shrubs in no. 8). 



Stamens numerous, much exserted; corolla sympetalous; flowers in heads or spikes; leaves 

 bipinnate. 



Stamens monadelphous; unarmed bush 1- Calliandra. 



Stamens distinct ; spiny shrub 2. ACACIA. 



Stamens 10; corolla choripetalous (except 1 species of no. 4). 



Leaves simple; flowers red-purple; cisniontane shrub 3. Cercis. 



Leaves compound ; deserts. 



Flowers sessile in dense cylindric spikes; corolla minute (1 to 1% lines long) ; leaves 



usually twice pinnate; desert trees 4. Prosopis. 



Flowers in racemes. 



Fertile stamens 7, the sterile 3 ; anthers fixed by the base ; leaves simply pmnate ; 



low bushes ^- Cassia. 



Stamens 10, all fertile; anthers fixed by the middle; leaves bipinnate. 

 Trees ; calyx -lobes soon reflexed, deciduous. 



Pods flattish; leafy branches with axillary thorns 6. Cercidium. 



Pods torulose; branches without axillary thorns (in ours) 



7. Parkinsonia. 

 Shrubs or low herbs; calyx-lobes not reflexed, persistent 8. Hoffmanseggia. 



B. Corolla papilionaceous. 



1. Stamens distinct; leaves palmately 3-foliolate. 



Flowers yellow, in racemes; stipules conspicuous; herbs 9. Thermopsis. 



Flowers purple, solitary; stipules none; very spiny shrub 10. Pickeringia. 



