78 RUTACEAE 



PONCIRUS. Hardy or Deciduous Orange. 

 Deciduous shrub with pale firm wood with minute diffused 

 ducts and fine medullary rays; strong tortuously 3-sided and 

 compressed green twig& with solitary large compressed axillary 

 spines; more or less compressed continuous relatively large 

 white pith; alternate minute low half-round leaf-scars with a 

 single indistinct compound bundle-trace; no end-bud or stipule- 

 scars; small hemispherical finally red sessile solitary buds 

 with about 4 exposed scales; trifoliolate pellucid^punctate 

 leaves; moderately small perfect polypetalous white flowers 

 solitary or paired in the axils in early spring; and orange-like 

 fruit 4 cm. in diameter. Sometimes placed in Citrus. 

 Vegetative parts glabrous : fruit velvety. P. trifoliata. 



PTELEA. Hop Tree. 



Deciduous shrubs or small trees with soft wood with larger 

 crowded vernal ducts and small summer ducts in wavy tan- 

 gential patterns, and fine medullary rays; rather slender 

 roundish twigs with round continuous pith; alternate litMe- 

 raised finally horseshoe-shaped leaf-scars with 3 bundle-traces; 

 no stipule-scars; small hairy superposed lateral buds but no 

 end bud; palmately trifoliolate stalked leaves with large near- 

 ly entire pellucid-punctate leaflets; rather small perfect open 

 polypetalous flowers in compound corymbs; and densely clus- 

 tered slender-pedicelled round veiny samaras. 



1. Twigs glabrous. 2. 



Twigs finely tomentose. P. trifoliata mollis. 



2. Leaves green. (Wafer ash). P. trifoliata. 

 Leaves 1 yellow. P. trifoliata aurea. 



PHELLODENDRON. Cork Tree. 



Small deciduous trees with soft-corky bark; brown wood 

 with rather large ducts crowded in the spring wood and minute 

 ducts in wavy tangential lines in summer, and fine medullary 

 rays; rather stout rounded twigs; crenate continuous white 

 pith; opposite or alternate, but then 4-ranked, somewhat eleva- 

 ted horseshoe shaped leaf-scars w.ih 3 simple or compound 



