416 
ORIGIN OF LIFE IN AMERICA 
Mountain arctic alpine region reappear in the extra-tropical 
Andes, being, so far as is known, wholly absent from the 
Mexican Mountains as well as from the tropical Andes. 
Among these Professor Bray mentions particularly Gentiana 
prostrata, Trisetum subspicatum, Primula farinosa and its 
variety magellanica, Draba incana, Alopecurus alpinus, Saxi- 
fraga caespitosa, Polemonium microcanthum and Collomia 
gracilis. Dr. Stapf kindly drew my attention to another 
instance, namely, to the occurrence on the mountains of 
Argentina, at a height of 10,000 feet, of the typically arctic 
genus of grasses Phippsia. The similarity in the flora of the 
two regions is by no means confined to mountain forms. 
Some species of the western plains of North America plso 
reappear in the extreme south of South America. Thus the 
monotypical saxifrage Lepuropetalon, a peculiar and some¬ 
what abnormal genus, grows in damp low-lying meadows in 
Texas. Yet far south on the coast of Chile the same species, 
Lepuropetalon spathulatum is to he met with. 
A few of these plants may possibly have been casually in¬ 
troduced from the northern locality to the southern. But in 
most cases, Professor Bray * thinks, we have to deal with 
forms which were connected by a remote ancestry, and which 
flourished at a time and under conditions permitting a more 
general distribution. 
What these conditions were like he does not venture to sug¬ 
gest, hut a direct land bridge between western North America 
and Chile probably existed, as I suggested, in late Cretaceous 
and early Tertiary times. To it, I think, the relationship 
of the floras of these two widely separated areas to one 
another, is mostly due. Whether many species of plants 
have persisted to the present day from such remote times 
we do not know. Some no doubt have, and, as already 
stated, others, among them those alluded to, may have 
done so. A large portion of this old western land, with' 
its mixture of a southern and northern fauna and flora, 
evidently remained above sea-level until a much later geo¬ 
logical period. The evidence derived from certain relict 
land-areas of this Pacific land belt clearly shows that a 
* Bray W.'L., “ Eelations of North American Flora,” pp. 709—716. 
