BARTRAM: BOTANIZING IN SOUTHERN ARIZONA 247 
OPUNTIA ARBORESCENS Engelm. Forming impenetrable thickets on 
the plains. 
OPUNTIA LEPTOCAULIS DC. The common _ slender stemmed cholla 
of the regio 
parent: BicELovil Engelm. Frequent on arid rocky slopes in the 
foothills. 
OPUNTIA CHOLOROTICA Engelm. & Bigel. On ledges near the mouth of 
Sabino Canyon 
OpuntTiA TouMEYI Rose. Frequent on the gravel plains. 
MAMILLARIA GRAHAMI Engelm. Frequent in small colonies among 
rocks in ee foothills. The diminutive scarlet pipe-shaped fruits are very 
attractive 
Ecu ACTUS WISLIZENI Engelm. Eola sparingly over the foot- 
hill sie een plants are well over a meter eight. 
ECHINOCEREUS FENDLERI (Engelm.) Riimpl. Forming clumps in 
gravel plains near the foothills. 
CEREUS GIGANTEUS Engelm. The sahuaro well merits the reputation of 
being one of the most unique and striking elements of the desert vegetation. 
Daucus PpusmLLus Mx. Scarce on shaded knolls in the washes. 
PLUMBAGO SCANDENS L. In the foothills of the Santa Catalina Moun- 
tains. Leaves and fruit persistent. 
FORESTERIA PHILLYREOIDES Torr. This is a Mexican type and Dr. 
Standley informs me they have but one other specimen from the United 
States, collected at Tucson by Pringle. The staminate flowers were fully 
developed by December 3oth and a few leafy shoots supplied the foliage 
characters. On rocky slopes along the Ajo road west of Tucson. 
FRAXINUS ATTENUATA Jones. Inthe mouth of Sabino Canyon. 
MENODORA SCABRA Gray. On arid slopes of the Tucson Mountains. 
HAPLOPHYTON CImMicIpDUM A. DC. Rare on rocky talus slopes at 
Robles Pas 
ASCLEPIAS LINARIA Cav. Frequent on ledges in the lower slopes of 
the Santa Catalina Mountains 
PHILIBERTELLA LINEARIS Geass Twining over bushes on dry rocky hill- 
sides 
EVOLVULUS LINIFOLIUS L. An inconspicuous little perenial with fugitive 
flowers. Frequent among rocks and dry ledges in the foothills. 
JACQUEMONTIA PRINGLEI Gray. Not uncommon on rocky hillsides. 
Leaves and capsules persistent. 
ECTOCARYA LINEARIS (R. & P.) DC. Locally abundant on a gravel 
shelf near Picture Rocks. 
AMSINCKIA Menzigesu (Lehm.) Nels. & Macb. Flowering with Thys- 
anocarpus and nue on shaded ledges at Picture Rocks. 
