198 ALBAN STEWART 



It was actually cold there, and this was in the month of March 

 before the coolest part of the year had begun. Air temperatures 

 below 70° F. are not at all uncommon at sea level. 



The forms of Euphorbia viminea, which Scharff 14 discusses at 

 some length, have little bearing on the subject of origin if we 

 admit the possibility of a former union of the islands with each 

 other but not with the mainland. If he had taken the trouble 

 to examine the latest flora of these islands 15 he would have found 

 that two of the forms described for this species have already 

 been collected upon more than one of the islands. I believe 

 that this will eventually have but little to do with the subject 

 anyhow because there is some question about the distinctness 

 of some of the so-called Galapagos Island forms. In fact I 

 will shortly show that they do not exist in one of the species 

 in which varietal forms have been described. We are jlealing 

 upon these islands with a variety of climatic conditions as well 

 as different kinds of soil. It is often the case that a few hun- 

 dred feet difference in elevation will show almost an entire change 

 in the character of the vegetation, from extremely xerophytic 

 to mesophytic types. A considerable number of species are 

 not confined to any one of such zones, however, but may occur 

 to a greater or less extent in all of them, with a corresponding 

 change in habit and general appearance in each. 16 Some of the 

 species which occur near sea level as mere bushes, assume the 

 size of forest trees in the moister interior regions of the islands. 

 Such marked changes in stature have a corresponding effect upon 

 the length of internodes, size of the leaves, etc. Formal differ- 

 ences are of course very slight, and it is rather unsafe to establish 

 them in woody species which may occur under a variety of con- 

 ditions, unless we have a larger series of specimens upon which to 

 base them than has thus far been collected from Galapagos Islands. 



My own work on the flora of these islands is dismissed by 



14 L. c, pp. 314-335. 



15 Stewart, I. c, p. 93. 



16 See Stewart, I. c, p. 77 for changes brought about in the appearance of 

 Rhynchosia minima (L.) DC. by the different climatic conditions at different 

 elevations. 



