FOSSIL PLANTS OF ARGENTINA 
415 
west coast of Chile which he considers to be of early Tertiary 
age. Of these the greater portion, he thinks, belongs to still 
existing species, though he hesitates, in the absence of further 
evidence, to adopt the recent specific names. At any rate, 
almost all are very closely related to species now living in 
the West Indies, Central America and Brazil. 
There exists a very widespread assumption that no species 
of animals or plants survive to this day from the Mesozoic 
Era. As our knowledge of fossil animals increases, instances 
accumulate of very close resemblance of Mesozoic species of 
mollusks to those now living, while some genera certainly 
date back to Palaeozoic times, so that we can no longer place 
implicit faith in the old traditional belief. My own convic¬ 
tion is that, many species of the less highly organised groups 
of animals have survived unchanged even from those remote 
times to the present day. We know that certain species of 
plants such as Sequoia langsdorfi, and some of the Unios 
among animals, have remained practically unaltered through¬ 
out a series of geological ages. It seems equally possible 
that others of whose geological history we know nothing have 
likewise done so. 
Professor Asa Gray and Sir Joseph Hooker * long ago 
directed attention to the unexpected feature that many genera, 
and even species of North American plants, recur in the dis¬ 
tant regions of southern South America. More recently 
Professors Engler,f Bray and Hackel have dwelt on this re¬ 
markable phenomenon, and have speculated on the problems 
connected with it. The flora of the Rocky Mountains, 
including the Sierra Nevada Mountains above the transition 
zone, and the mountains of Chile and Argentina, though 
separated from one another by a stretch of some ten degrees of 
latitude of moist tropical country, abound in northern genera 
of plants, such as Ranunculus, Anemone, Geranium, Spiraea, 
Geum, Rubus, Saxifraga, Vaccinium, Gentiana, Hieracium 
and others. The greater number of such plants occurring in 
the southern continent are endemic, pointing to long-con¬ 
tinued isolation. Yet certain species even of the Rocky 
* Gray, Asa, and J. Hooker, “Vegetation des Rocky Mountain Ge- 
bietes,” p. 292. 
t Engler, A., “ Entwicklungsgeschichte der Florengebiete,” II., p. 2.'>6. 
