136 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 13 



Puerto Escondido, February 11, Dawson 1102. Los Angeles Bay, 

 March 19, 20, Rempel 237. Island in Concepcion Bay, March 16, 

 Rempel 203, on fan. 



Arid desert slopes around the Gulf of California on the peninsula 

 and on the mainland. 



Larrea tridentata (DC.) Cov., C.N.H. 4:75. 1893. 

 Los Angeles Bay, March 19, 20, Rempel 242. 

 Found in nearly all the hot American deserts. 



Viscainoa geniculata (Kell.) Greene, Pittonia 1:163. 1888. 



Los Angeles Bay, March 19, 20, Rempel 241. Puerto Refugio, Angel 

 de la Guardia Island, March 20, Rempel 277. 



An irregular branching shrub along rocky arroyos of the southern 

 two-thirds of the peninsula, along the mid-Sonoran coast, and known 

 also from Tiburon Island. Rempel 277 appears to represent the first 

 record from Angel de la Guardia Island. 



Simarubaceae 



Castela peninsularis Rose, C.N.H. 12:278. 1909. 



San Gabriel Bay, Espiritu Santo Island, March, Rempel 85 (sterile) 



A low stiff spiny shrub with sclerophyllous drought-deciduous and 

 rather ephemeral leaves, the branches varying from yellowish green to 

 reddish purple, the whole pubescent except the spines. It is known from 

 the southern part of the peninsula from Magdalena Bay and near Mu- 

 leje southward; the type from San Jose del Cabo. Johnston (Proc. Calif. 

 Acad. Sci. IV, 12:1056) collected it on several of the adjacent gulf 

 islands from Catalina south. 



BURSERACEAE 



Bursera Hindsiana (Benth.) Engl, in DC, Monogr. 4:58. 1883. 



Bursera rhoifolia (Benth.) Jtn., Proc. Calif. Acad. Sci. IV, 12:1058. 

 1924. 



West cove in Concepcion Bay, March 15, Rempel 181, low shrub or 

 tree on rocky slopes. Puerto Refugio, Angel de la Guardia Island, March 

 20, Rempel 267a. Los Angeles Bay, March 19, 20, Rempel 234a. Tor- 

 tuga Island, March 17, Rempel 229. 



A thick-butted and usually dwarf tree with thick reddish or gray 

 branches and spur branchlets. The leaves are quite variable; simple, or 

 partially trifoliate, or distinctly trifoliate, as on the Tortuga specimen 

 (up to 7 cm long) or sm.all, as on the Concepcion Bay sheet (10 to 15 

 mm long). As Bullock (Kew Bull. 1936:366) has pointed out, the 



