74 



SAXIFEAGACEAE. 



PHILADELPHUS. "Syringa". Mock Orange. 

 (Family Saxifragaceae). 



Shrubs, mostly with exfoliating 

 outer cortex: deciduous. Twigs 

 more or less lined or obscurely 

 hexagonal: pith moderate, round- 

 ed, pale, continuous. Buds soli- 

 tary, sessile with 2 nearly valvate 

 mostly hairy scales, the end-bud 

 lacking. Leaf-scars opposite or 

 exceptionally in whorls of 3, half- 

 round with a thin membrane more 

 or less covering the bud, or cres- 

 cent-shaped when this is burst, 

 connected transversely: bundle- 

 traces 3: stipule-scars lacking. 

 References under Decumaria. 



1. Outer cortex persistent, becom- 



ing gray. 2. 



Outer cortex straw-colored or 

 red, quickly exfoliating. 3. 



2. Membrane tough. 



(1). P. pubescens. 

 Membrane thin. (2) . P. Lewisii. 



3. Leaf-scar scarcely reaching the end of bud. 4. 

 Leaf-scar broad, covering the bud until burst. 7. 



4. Leaf-scar narrow: twigs slender. 5. 



Leaf-scar broad: twigs moderate. P. californicus. 



5. Twigs glabrous. (3). P. microphyllus. 

 Twigs more or less villous or canescent. 6. 



6. Pubescence scanty: buds half-covered. X P. Lemoinei. 

 Pubescence abundant: buds fully exposed. 



(4). P. hirsutus. 



7. Twigs more or less villous: fruit racemed. P. coronarius. 

 Twigs glabrous: fruit nearly solitary. (5). P. inodorus. 



