PIjANTS OF SOUTHERN, NEW JERSEY. 519 



ZANTHOXYLUM L. 

 Zanthoxylum americanum Mill. Prickly Ash. 



Zantholoxylum americanum Miller, Card. Diet. Ed. 8. No. 2. 1768 IfSouth 

 Carolina] . 



Xanthoxylon Americamum Britten 74. — Keller and Brown 209. 



Locally common in the northern counties, but very rare in 



our region; reported but once within our limits — Freehold, on 



authority of Willis. 



PTELEA L. 

 Ptelea trifoliata L. Three-leaved Hop Tree. 



Ptelea trifoliata Linnasus, Sp. PI. 118. 1753 [ Virginia] .—Britton 74. 



Woodlands in the Delaware Valley; rare. Found on Ridge's 

 Island, Hunterdon County, and on the banks of Crosswick's 

 Creek, both in Mfercer County, by C. C. Abbott (Britton's 

 Catalogue) and Burlington by A. C. Apgar, who collected a speci- 

 men near Borden town, which is now in the N;. J. Geological 

 Survey herbarium! at New Brunswick. This tree has almost 

 precisely the samle distribution as the Judas, both of them south- 

 ern species, which find their northern limit in these river valleys, 

 but which cannot establish themselves below the head of tide- 

 water, probably on account of the lack of steep, wooded banks. 

 Fl. — 'Late May to mid-June. Fr. — September to October. 

 Middle District. — Bordentown (NB). 



Family PO'LlYQAIACE^. Milkworts. 



Key to the Species. 



a. Flowers in spikes or spike-like racemes at the summit of the stewi or its 

 branches. 

 b. Basal leaves spatulate, flowers orange yellow. . Polygala lutea, p. 520 

 bb. Basal leaves inconspicuous or wanting, flowers not yellow. 

 c. I<eaves, some at least verticillate. 

 d. Spikes 4-6 mm. thick. 



e. Most of the leaves in whorls, flowers greenish white. 



P. verticillata, p. 522 

 ee. Most of the leaves' alternate, only the lowest in whorls, 

 flowers usually slightly pink tinted. P. ambigua, p. 522 



dd. Spikes 8-18 mm. thick. 



e. Spikes sessile or nearly so, wings deltoid, flowers purple 



or greenish white. P. cruciata, p. 521 



ee. Spikes peduncled, leaves less regularly verticillate, wings 



lanceolate ovate, flowers purple. P. brevifolia, p. S21 



CO. Leaves all alternate. 



