240 PROCEEDINGS OF THE AMERICAN ACADEMY, 
for the introduced species are for the most part the plants of the West 
Indian Islands and of the lower hot parts of the South American coast, 
whilst the peculiar Flora is chiefly made up of species not allied to 
the introduced, but to the vegetation which occurs in the Cordillera or 
the extra-tropical parts of America.” But, after repeated efforts, I am 
unable to verify this double relationship, and must infer that subsequent 
discoveries, both upon the mainland and upon the islands, have done much 
to weaken the grounds upon which these conclusions once rested. Many 
cases could now be cited to show that the endemic plants of the Gala- 
pagos Islands, far from forming a marked or peculiar class, are often the 
nearest allies of species or varieties which are common to the islands and 
the continent. Both classes include alike the most widely diverse ele- 
ments, — xerophytic, mesophytic, and halophytic types, annuals and peren- 
nials, herbs, shrubs, and trees, climbers and epiphytes, —and both occur 1n 
common at all altitudes and in every sort of habitat the islands afford. 
Accordingly it is not remarkable to find their closest congeners occupying 
the same diverse habitats upon the mainland from the hot, moist lowlands 
about Guayaquil and Panama to the cool parts of the Andes, dry regions 
of Peru or western Mexico, and in a few instances the more fertile up- 
lands of Colombia, Central America, and Mexico. Moreover, the 
endemic forms show all grades of differentiation from their continental 
allies ; some are well marked specific types, others mere varieties, while 
still others are scarcely distinguishable forms. 
It appears, therefore, that very diverse floral elements have reached 
the archipelago, probably at different times and from widely different 
habitats. Presumably all have been subjected on the islands to influences 
of a kind to bring about change in their nature; and in two-fifths of the 
plants now known on the islands more or less pronounced evidences of 
such change can be observed. These plants, which show modification, 
form, as we have seen, no sharply marked class, but pass over very imper 2 
ceptibly into nearly related forms which it is impossible to differentiate 
from plants of the mainland. That some plants have reached the Gala- 
pagos from the West Indian Islunds during the subsidence of the Isthmus 
of Panama is by no means impossible, but as we should expect, these 
plants, if such there were, have established themselves in like manner 
upon the western coast and slopes of the continent, so that it is now — 
quite impossible to trace any direct floral affinity between the West 
Indies and the Galapagos which the latter do not exhibit even in a higher 
degree with the western parts of the mainland. 
Mr. Hemsley has already commented upon the wide divergence be- 
ff Peeerseulesior sigs ct g tes ies 
