158 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 13 



Opuntia aff. Wilcoxii Brit. & Rose, Cactaceae 1 :172. 1919. 

 San Pedro Nolasco Island, March 29, Rempel 306, 

 West coast of Mexico in southern Sonora and northern Sinaloa; 

 type from Fuerte in northern Sinaloa. This first insular collection ap- 

 pears to be in good character with the species. It was just coming into 

 flower when collected. Unusual are the areoles around the edge of the 

 joints; they are larger and with longer glochids than those on the flat 

 faces. 



Opuntia sp. 



Dawson 1091 from Puerto Escondido, Baja California, collected in 

 a sterile condition February 11, 1940, is a flat-jointed Opuntia resemb- 

 ling O. tardispina Griffiths from eastern Texas, as illustrated in Brit. & 

 Rose (I.e. p. 141). Doubtless, this is one of the unknown Opuntiae men- 

 tioned by Johnston (Proc. Calif. Acad. Sci. IV, 12:1117). 



Pachycereus Pringlei (Wats.) Brit. & Rose, C.N.H. 12:422. 

 1909. 



South end of Tiburon Island, March 27, Rempel 298 (sterile). 



Abundant over wide areas through middle and southern Baja Cali- 

 fornia, on the gulf islands, on the cerros southwest of Altar in north- 

 western Sonora, and in the hills about Guaymas, Sonora; type from the 

 Altar River, Sonora. Its western limit is Cedros Island, where it was 

 recently discovered by Howell (Leafl. West. Bot. 3:183. 1942). 



Sterile nubbins represented by Rempel 211, 307, 317, from Tortuga 

 Island, San Pedro Nolasco Island, and Fraile Bay respectively, are either 

 referrable to this plant or to Pachycereus pecten-ahoriginum, the other 

 giant cactus abundant through the southern part of the gulf region. 



Rathbunia alamosensis (Coult.) Brit. & Rose, C.N.H. 12:415. 

 1909. 



Ensenada de San Francisco, Sonora, March 30, Rempel 314. Near 

 Guaymas, Sonora, January 23, Dawson 1074. 



Coastal lowlands from southern Sonora to Nayarit; type from 

 Alamos, Sonora. It commonly forms colonies several yards in diameter, 

 spreading by declining or broken stems taking root. It is also employed 

 locally and effectively for making fences, the cuttings taking root readily 

 and eventually forming a dense hedge row. 



Rhizophora mangle L., Sp. PI. 443. 1753. 



West Cove in Concepcion Bay, March 15, Rempel 174. 



