NO. 2 gentry: land plants 151 



Machaerocereus gummosus (Engelm.) Brit. & Rose, Cactaceae 

 2:116. 1920. 



Puerto Escondido, Dawson 1109, abundant over all brush-land. 

 Fraile Bay, Rempel 323, Tortuga Island, Rempel 210. 



Common and widespread through Baja California south of Ensen- 

 ada and on the adjacent islands; type from northwestern Baja Cali- 

 fornia. In places it is abundant and is a codominant with other desert 

 shrubs. 



Mammillaria albicans (Brit. & Rose) Berger, Kakteen, 308. 

 1929. 



San Pedro Nolasco Island, February 6, 1940, Dawson 1039. 



Recorded only from Santa Cruz, San Jose, and San Pedro Nolasco 

 Islands, the above cited specimen being new to the known flora of the 

 latter island. Referred here doubtfully is Rempel 302 also from San 

 Pedro Nolasco Island. It is a smaller, slenderer plant with an evident 

 tendency to be cespitose. 



Mammillaria angelensis Craig, Mam. Handb. 165. 1945. 



Angel de la Guardia Island (probably Puerto Refugio), January 26, 

 Dawson sine no. Pond Island, February 5, Dawson sine no. Punta 

 Frailes, February 16, Dawson 1112. 



Known previously only from Angel de la Guardia Island, the species 

 is now certainly known from Pond Island, but Punta Frailes collection 

 (sterile) is doubtfully referred to this species. The long reflexed petals 

 are singularly characteristic of this species. 



Mammillaria dioica K. Brge., Erythea 5:115. 1897. 

 Tiburon Island, January 25, Dawson 1018. 



Apparently ranges throughout Baja California, but hitherto not re- 

 ported for any of the California Gulf Islands. 



Mammillaria Evermanniana (Brit. & Rose) Orcutt, Cactogra- 

 phy 7. 1926. 



Canyon above Puerto Escondido, Sierra Giganta scarp, Rempel 144j 

 sides of canyon. 



Along the Sierra Giganta scarp in southern Baja California and 

 adjacent islands; type from Ceralbo Island. Craig (Mam. Handb. 82. 

 1945) states, but without citation, that it is also reported from San Pedro 

 Nolasco Island. It is a small globose plant 6 to 10 cm high preferring 

 humic soils in the detrital pockets of rocky terrain. It is rare in both 

 living and herbarium collections. 



