FLORA OF THE DISTRICT OF COLUMBIA. 185 



10. ROBINIA L. 

 1. Sobinia pseudo-acacia L. Black locust. 



Abundant; perhaps naturalized. May. Pa. to Iowa and Ga. 

 A tree is shown in plate 33. 

 Several other species of the genus are frequent in cultivation. 



11. ASTRAGALUS L. 



1. Astragalus carolinianus L. Milk vetch. 



Low ground along the upper Potomac. June- July. Northern states, south to Ga. 

 {A. canadensis L.) 



12. STYLOSANTHES Swartz. Pencil flower. 



Leaflets oblong-linear to oblanceolate, the larger ones 3 cm. long or longer, usuallj' 

 very acute; bracts subtending the flowers entire; plants very bristly. 



1. S. biflora. 



Leaflets oval or elliptic, mostly less than 2 cm. long, usually rounded or obtu.se at the 

 apex; bracts 3-parted; plants only slightly bristly 2. S. riparla. 



1. Stylosanthes biflora (L.) B.S.P. 



Dry soil; common. July-Sept. Eastern U. S. (S. elatior Swartz.) 



2. Stylosanthes riparia Kearney. 



Dry soil; occasional. June-Aug. Pa. to Ala. 



13. MEIBOMIA Heist. Tick trefoil. 



Stipules large, green, ovate or triangular, persistent. 

 Stems trailing. 

 Flowers purple; leaflets orbicular or nearly so; joints of the pod 3-5. 



4. M. michauxii. 

 Flowers whitish; leaflets broadly ovate; joints of the pod 2 or 3. . 5. M. ochroleuca. 

 Stems erect. 



Leaflets glabrous or nearly so, very acute 6. M. bracteosa. 



Leaflets hairy, very obtuse 7. M. canescens. 



Stipules small, brown, narrowly linear or subulate, often deciduous. 

 Pod borne on a stalk many times longer than the calyx, not lobed on the upper 

 margin, very deeply lobed on the lower margin, the joints 1-4. Stems usually 

 erect; plants nearly glabrous. 

 Flowering stems naked, rising from the base of the sterile leafy stems. 



1. M. nudiflora. 



Flowering stems leafy. 



Leaves scattered along the stems; leaflets obtuse 2. M. pauciflora. 



Leaves crowded at the top of the stem below the panicle ; leaflets taper-poin ted . 



3. M. grandiflora. 

 Pod sessile, or borne on a short stalk only 2 or 3 times as long as the calyx, lobed 

 on both margins but much more deeply so below than above. 

 Leaflets small, most of them less than 2.5 cm. long, rounded at thef apex; joints 

 of the pod 2 or 3. 

 Plants glabrous or nearly so; petioles about as long as the lateral leaflets. 



14. M. marylandica. 

 Plants copiously hairy; petioles usually much shorter than the lateral leaflets. 



15. M. obtusa. 



Leaflets larger, most of them more than 3 cm. long, usually much larger; joints 



of the pod often more numerous. 



Stems and leaves glabrous or nearly so. Joints of the pod 4-6. 



Leaflets lanceolate or oblong, all or most of them less than 2 cm. wide, gi-een 



beneath 8. M. paniculata. 



