488 BOTANICAL GAZETTE [JUNE 
In the lower eocene flora of the Mississippi embayment region 
there are six well marked species of Myrcia and four nearly equally 
well marked species of Eugenia, as well as a single species of Calyp- 
tranthes. The latter genus appears also to be represented in recent 
collections from the Oligocene of the Isthmus of Panama. Without 
pursuing the subject beyond the known facts, confessedly meager, 
and noting the presence in our lower eocene flora of numerous 
Combretaceae based upon leaves, flowers, and fruits, and a repre- 
sentative of the great tropical family Melastomaceae, largely 
American in the existing flora, both of which are families closely 
related morphologically to the Myrtaceae, it would seem that the 
known facts, as well as the law of probabilities, suggest America 
as the original home of the family. That in its early deployment 
it reached Europe, either by way of Asia or the North Atlantic 
plateau, early in the Upper Cretaceous, and became cosmopolitan 
before the close of the Cretaceous seems a most probable hypothesis. 
During the late Tertiary this ancestral stock, which largely coincided 
with the existing subfamily Myrtoideae, was forced to withdraw 
from temperate North America to the American tropics, where it 
had originated and to which it has since been so largely confined. 
The types peculiar to the Australian region represent the relics 
of the cretaceous radiation with numerous new types evolved on 
that continent in the manner that ANDREWS has suggested, and at 
a comparatively recent date geologically. This is exactly the 
reverse of the hypothesis proposed by DEANE (op. cit.), but one 
that accords far better not only with the facts of geologic history, 
but also with those of existing distribution. 
All of the American lower eocene forms are coastal types closely 
related to existing American species of similar habitat. 
About 150 fossil forms have been referred to the family Myr- 
taceae, one-third at least having been described as species of 
Eucalyptus. At least half of these occur in the Cretaceous of all 
parts of the world, but particularly throughout the Northern 
Hemisphere. They are especially well represented in North 
America, and the possibility that they are ancestral forms of 
Myrcia or Eugenia has already been pointed out. A similar wide- 
spread distribution but less specific variation characterizes the 
