POLYGALACEAE. 209 



1. XANTHOXYLUM L. 



1. XANTHOXYLUM Americanum Mill. Northern Prickly Ash, Toothache- 

 tree, M. p. 581. Rocky woods and river banks. Spring. 

 Philadelphia — Stenton (Br.), Woodlands Cemetery (Ha,), 46th and 

 Walnut streets, Gray's Lane and Rabbit's Lane, W. Philadelphia (Mac), 

 Mayland's Garden (Te.), Angora (VP.), near Gray's Ferry (Wn.). 

 Buclcs — Rock Hill (Fr.). Montgomery — Tylersport (Ja.), Sumneytown 

 (VP.), Uhl's Mill (Wn.). i^etouwe-Middletown (S. Tr.), Concord (W. 

 Tr.), Lancaster— {V.). Berks— (P.). Northampton— {P.). 

 Monmouth— FTeehold (C). Hunterdon— ^osemont (C). 



XANTHOXYLUM Clava-Herculis L. Southcm Prickly Ash. M. p. 

 581. Sandy soil; from the South. 

 Delaware— Painter 's Arboretum (Fu.). 



2. PTELEA L. 

 1. Ptelea trifoliata L. Shrubby Trefoil, Hop-tree. M. p. 581. Woods. 

 Early summer. 

 PTiitodeipWa— West Philadelphia, Gray 's Ferry (Cr.). jB«c/cs— Ridge '3 

 Island, Delaware river (Fr.), Stover's Island, Moyer (Fr.), near Morris- 

 vilie (Ws.). Z>da«;are— Concord (W. Tr.). Berks— {P.). Northampton 

 — Easton, Porter (B. C). 

 Mercer— Crosswick's Creek (C). Hunterdon — B,idge Island (C). 

 New Castle — Becoming frequent about nurseries, 18th street. 



Family 6. SIMARUBACEAE DC. Ailanthus Family. 

 1. AILANTHUS Desf. 

 1, Ailanthus glandulosus Desf. Tree of Heaven. M. p. 582. Cultivated 

 and escaped. Early summer. 



Family 7. POLYGALACEAE Reichenb. Milkwort Family. 



1. POLYGALA L. Milkwort. 



Flowers in solitary spikes or spike-like racemes, terminating the stem and 

 branches. 

 Basal leaves spatulate or obovate; flowers orange-yellow. 



1. P. lutea. 

 Basal leaves inconspicuous or wanting ; flowers not yellow. 



Leaves, at least the lower, verticillate ; spikes 8-18 mm. thick, blunt ; 

 flowers purple to greenish-white. 

 Spikes sessile or nearly so; wings deltoid. 2. P. cruciata. 

 Spikes peduncled; wings lanceolate-ovate. 3. P. brevifolin. 

 Leaves verticillate and alternate; spikes 4-6 mm. thick, acute. 



Verticillate leaves predominating; spikes dense; flowers green 

 to purplish. 4. P. verticillata. 



Alternate leaves predominating; spikes loose, long; flowers 

 more purple. 5. P. ambigua. 



Leaves all alternate. 



Petals united into a cleft-tube 6-8 mm. long; flowers pink. 



6. P. incarnata. 

 Petals not conspicuously united into a tube. 



Spikes ovoid to globose. 



Bracts persistent; flowers rose-purple to white. 



7. P. viridescens. 



