RUTACEAE. 



169 



PONGIRUS. Hardy Orange. 

 (Family Rutaceae). 



Shrubs with branch-spines: de- 

 ciduous. Twigs triangular, di- 

 lated into the thorns at the nodes, 

 rather stout: pith rather large, 

 white, homogeneous. Buds rather 

 small, solitary, sessile, subglobose, 

 with about 3 exposed scales, the 

 end-bud absent. Leaf-scars very 

 small, alternate, 5-ranked, half- 

 elliptical, scarcely raised: bundle- 

 trace 1, crescent-shaped, evanes- 

 cent: stipule-scars lacking. (Aegle, 

 Citrus}. 



The hardy orange, capable of 

 growth even in the North as an 

 effective and attractive hedge- 

 plant, presents another instance 

 of the occasional occurrence of 

 hybridization between different 

 genera, and at the same time em- 

 phasizes the closeness of the re- 

 lationship of such genera. Poncirus gives hybrids, more or 

 less intermediate in character, with the grape fruit belonging 

 to the evergreen unifoliolate genus for which the name Citrus 

 is now reserved; but it has been considered itself to belong 

 to that genus by botanists for whom generic characters might 

 be drawn a little more broadly than they are under the pre- 

 vailing custom. Its winter-characters are pictured by Schnei- 

 der, f. 85. 



For the hybrid "citranges" the generic name X Ponciro- 

 citrus might find appropriate use. 

 Twigs glabrous, glossy green: buds glabrous, blood-red. 



P. trifoliata. 



