66 Introduction to Botany. 



U. TRIFOLIUM. Clover or Trefoil. 



(L., tn\ three; /oUwn, leaf.) 



Herbs, with mostly slender branches and 3-foliate leaves, the leaflets 

 denticulate. Flowers pink, purple, white, or yellow, papilionaceous. 

 Stamens 10, diadelphous, or sometimes all united near the base. 

 Flowers in heads or spikes, and pods straight and membranaceous. 



±. Trifolium pratense, L. (L., pratensis, growing in a meadow.) Red or 

 Meadow Clover. Flowers red purple, sessile, in globose or ovoid heads, the 

 heads nearly or quite sessile. Somewhat pubescent, branching, perennial herbs. 

 Leaflets short-stalked from the same point, often dark-spotted near the middle. In 

 fields and meadows. 



a. Trifolium repens, L. (L., repens, creeping.) WHITE CLOVER. Creeping, 

 mostly glabrous perennials, rooting at the nodes. Leaves rising on long petioles; 

 leaflets obovate, emarginate-denticulate. Flowers white, in globose heads borne 

 on long peduncles ; flowers of the head raised on pedicels. In fields and open 

 places. 



m. PSORALEA. 



{Gr.,psoraleos, scurfy, alluding to glandular dots of the leaves.) 



Herbs or shrubs, with 1-5-foliate, glandular-dotted leaves. Flowers 

 bluish purple or white, borne mostly in spikes or racemes. Calyx 

 5-cleft, the lower lobe longest. Stamens diadelphous, sometimes 

 monadelphous. Ovary i-ovuled ; the short pod ovoid and indehiscent. 



1. Psoralea tenuiflora, Pursh. (L., tenuis, slender, small ; Jlos, Jloris, flower.) 

 Few-flowered Psoralea. Erect and slender, 2 to 4 feet high, hoary with an 

 appressed pubescence. Leaves short-petioled, digitately 3-5-foliate, mostly oblong- 

 oval or elliptic or obovate, sometimes mucronate at the apex. Peduncles slender 

 and much exceeding the leaves, loosely 6-14-flowered. Corolla purplish ; corolla 

 about twice the length of the calyx. Prairies. 



2. Psoralea argoph^Ua, Pursh. (Gr., argos, white; phyllon, leaf.) Silver- 

 leaf Psoralea. Silvery pubescent with white appressed hairs, i to 3 feet tall. 

 Petioles about equaling the leaves. Leaflets 3-5, digitate, oblong-oval to oblong- 

 obovate. Inflorescence interrupted-spicate, peduncles much exceeding the leaves. 

 Flowers deep blue or purplish, about \ inch long. Calyx lobes lanceolate, very 

 densely pubescent. Pod ovate, with a straight beak. On prairies. 



3. Psoralea floribiinda, Nutt. (\j.,flos, Jloris, flower -|- adjectival ending, signi- 

 fying plenty.) MANY-FLOWERED Psoralea. Stems much branched, i to 4 feet 

 high, hoary, not glandular. Leaves mostly 3-5-foliate, sometimes 7-foliate. Leaflets 

 oblong, canescent beneath and glandular on both surfaces. Peduncles 2 to 7 inches 

 long, usually many-flowered. Lobes of the calyx triangular-acute. Prairies. 



4. Psoralea escul^nta, Pursh. (L., esculeiitus, edible.) Pomme BLANCHE, 



