Volume 1

Scientific papers of Asa Gray / selected by Charles Sprague Sargent.

  • Gray, Asa, 1810-1888
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Scientific papers of Asa Gray / selected by Charles Sprague Sargent. Source: Wellcome Collection.

    400/416 (page 388)
    RE VIE WS. “ When we consider that, although subsidence has prob- ably at various times separated the two portions of the con- tinent, the highlands of Mexico and Central America have, in all probability, served during long periods as a bridge over which some portions of the mountain vegetation may have been transferred from north to south, and vice versa, we are led to feel surprise rather at the separations now ex- isting than at the presence of many genera and of a few iden- tical species in the flora of the Andes and that of the Rocky Mountains. It is true that I have reckoned as Andean genera and species many that extend northward as far as Mexico ; and it may well be that that region, so rich in varied forms of vegetation, is the original home of some that now appear to be more fully developed in the mountain ranges of western North America. Among the widespread Ameri- can types we must note two natural orders whose original home may with some confidence be placed in the north- western part of the continent. The Polemoniacece, of which about 140 species belong to that region, are represented in the Andes by five species of Gilia, one of Collonia, and by the endemic genus Cantua. They have sent to the Old World two or three species of Phlox in northern Asia [we believe only one, and that not far over the border], and a single emigrant which has reached Britain, — the Jacob’s Ladder of old-fashioned gardens, — which maintains a strug- gling existence in several isolated spots in Europe. The other specially American family is that of the Hydrophyllacem, of which 12 genera are known in North America, but which is represented in the Andean chain by only four species of Phacelia.” The Loasacece illustrate the opposite course of migration. A list of the plants which Mr. Ball collected in the upper valley of the Rimac in the Peruvian Andes, with various an- notations and the characters of some new species, concludes the present interesting contribution to Andean Botany. We believe that a second paper upon the subject may be ex- pected. Two or three comments upon individual plants of the list will bring our review to a close.