NO. 2 gentry: land plants 71 



Sterculiaceae 



Waltheria aisiericana L., Sp. PI. 673. 1753. 



Sulphur Bay, Clarion Island, March 16, Elmore B9, among lava 

 boulders on dry slope. Braithwaite Bay, Socorro Island, March 18, El- 

 more C2, elev. 5 feet. 



Widely distributed in the warmer parts of the world, common 

 through Mexico. A low perennial herb, often pol^-podial, 5-8 dm high, 

 very aggressive on disturbed areas, and one of the most collected weeds 

 of tropical America. Its presence on even the remote Revilla Gigedo 

 Islands is not surprising. Elmore reports that only a few plants were 

 observed. 



Cactaceae 



Opuntia occidentalis Engelm. & Big., Proc. Am. Acad. Sci. 

 3:291. 1856. 



Braithwaite Bay, Socorro Island, March 18, Elmore CIO, in ba- 

 saltic canyon in between boulders where there is a little soil formed by 

 disintegrating lava. 



Southwestern California, northern Baja California, and the adjacent 

 islands along the maritime slopes; type from "western slopes of the 

 California Mountains." 



Elmore's collection is the first identifiable material of the Platy- 

 opuntia which has long been noted upon the slopes of Socorro. Although 

 sterile, his specimens exhibit only minor differences from California 

 plants, as reviewed by Dr. Clover, who made the determination. The 

 presence of this species appears to be another bit of evidence supporting 

 the theory of the dissemination of migrules by oceanic currents. The 

 relationship of the Revilla Gigedo plants to the flora of California and 

 means of dispersal has been discussed by Johnston (1931). 



COXVOLVULACEAE 



Ipomoea cathartica Poir., Encycl. Suppl. 4:633. 1816. 



Sulphur Bay, Clarion Island, March 16, Elmore B5, upper beach 

 in exposed sandy soil, flowers blue or purple. 



Common to the American tropical lowlands; among the Revilla 

 Gigedo it is known only from Clarion Island. 



BORAGINACEAE 



Heliotropium curassavicuini L., Sp. PI. 130. 1753. 



Sulphur Bay, Clarion Island, March 16, Elmore Bll, on edge of 

 fresh water lagoon. 



Common on saline or alkaline soils throughout most of tropical and 

 subtropical America. 



