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 Eocky Mountain Ge- 

 bietes," p. 292. 



t Engler, A., " Entwicklungsgeschichte der Florengebiete," .II., p. 2*>6. 



