STANDLEY TREES AND SHRUBS OF MEXICO. 321 



Erect shrub, the branches sometimes spinelike; leaves 0.5 to 1.5 cm. long; 

 petals white or purplish, 1 to 1.4 cm. long. 

 3. Crossosoma parviflorum Robins. & Fern. Proc. Amer. Acad. 30: 114. 1894. 



Sonora. Arizona, the type from the Grand Canyon. 



Shrub, 1 to 2.5 meters high ; leaves elliptic-oblong, 8 to 13 mm. long, pale 

 green ; petals vphite, 6 mm. long. 



60. ROSACEAE. Rose Family. 



Reference: Rydberg, N. Amer. Fl. 22: 239-533. 1908-1918. 

 Shrubs or trees; leaves usually alternate, simple or compound, commonly 

 stipulate; flow^ers usually perfect, often large and showy; sepals normally 5; 

 petals as many as the sepals or wanting ; stamens usually numerous ; fruit 

 of achenes, follicles, or small drupes. 



Many herbaceous plants of the family are natives of Mexico. 

 Leaves compound or deeply lobed and with linear lobes. 

 Petals none ; flowers in long spikelike racemes. Leaves pinnate, with 9 to 19 



leaflets; very low shrub 5. ACAENA. 



Petals present ; flowers never in spikelike racemes. 



Leaves 2 or 3 times pinnate, with very numerous minute divisions. Plants 

 unarmed ; flowers small, white, corymbose-paniculate. 



9. CHAMAEBATIA. 

 Leaves once pinnate or digitate or merely lobed. 



Leaves merely pinnate-lobed ; flowers mostly solitary ; plants unarmed. 



Bractlets present on the calyx ; pistils numerous 7. FALIiUGIA. 



Bractlets none; pistils few 8. COWANIA. 



Leaves pinnate or digitate; flowers often racemose, corymbose, or 

 paniculate; plants usually armed with spines. 

 Fruit of numerous druplets borne on a receptacle; leaves often 

 palmate; petals usually white; stipules free from the petiole. 



11. RUBUS. 

 Fruit globose or urceolate, with numerous achenes inside ; leaves pin- 

 nate ; petals pink or red ; stipules united to the petiole. 



12. ROSA. 

 Leaves simple, entire or dentate, or with short, broad lobes. 

 Leaves entire. Flowers white. 



Fruit of usually 3 follicles; leaves flat; flowers racemose 1. SPIRAEA. 



Fruit an achene ; leaves clavate or filiform ; flowers paniculate. 



6. ADENOSTOMA. 

 Leaves toothed or lobed. 

 Leaves digitately lobed ; fruit of numerous fleshy druplets. Flowers 



large, white 11. RUBUS. 



Leaves merely dentate or crenate or pinnately lobed ; fruit dry. 



Petals none; calyx tube long-tubular; fruit a single achene with a long 

 plumose tail ; flowers axillary, solitary or fasciculate. 



10. CERCOCARPUS. 

 Petals present ; calyx tube never tubular ; fruit of follicles or of more 



than one achene ; flowers terminal, often paniculate. 

 Fruit of achenes with long plumo.se tails ; flowers ochroleucous or 



purple 8. COWANIA. 



Fruit of follicles without long plumose tails ; flowers white. 



Stipules none ; seeds exalate ; leaves deciduous__4. SERICOTHECA. 



Stipules present, deciduous ; seeds winged ; leaves persistent. 



