- [Footnote: well as of Torreya, Salisburia adiantifolia, and Cephalotaxus
from among the Taxineæ, recalls forcibly the obscurity which still prevails in the conditions which have determined the original distribution of vegetable forms, a distribution which cannot be sufficiently and satisfactorily explained solely by similarity or diversity of soil, thermic relations, or meteorological phenomena. I remarked long ago that the Southern Hemisphere for example has many plants belonging to the natural family of Rosaceæ, but not a single species of the genus Rosa. We learn from Claude Gay that the Rosa chilensis described by Meyen is only a wild variety of the Rosa centifolia (Linn.), which has been for thousands of years a European plant. Such wild varieties, (i. e. varieties which have become wild) occupy large tracts of ground in Chili, near Valdivia and Osorno. (Gay, Flora Chilensis, p. 340.)
In the tropical region of the Northern hemisphere we also found only one single native rose, our Rosa montezumæ, in the Mexican highlands near Moran, at an elevation of 8760 (9336 Engl.) feet. It is one of the singular phenomena in the distribution of plants, that Chili, which has Palms, Pourretias, and many species of Cactus, has no Agave; although A. americana grows luxuriantly in Roussillon, near Nice, near Botzen and in Istria, having probably been introduced from the New Continent since the end of the 16th century, and in America itself forms a continuous tract of vegetation from Northern Mexico across the isthmus of Panama to the Southern part of Peru. I have long believed that Calceolarias were limited like Roses exclusively to one side of the Equator; of the 22 species which we]*
