272 ESSAYS. 
Glyptostrobus, Libocedrus, Pines of our five-leaved type, as 
well as the analogues of other American forms, several species 
of Juglans answering to the American forms, and the now 
peculiarly American genus Carya, Oaks of the American 
types, Myricas of the two American types, one or two Planer- 
trees, species of Populus answering to our Cottonwoods and 
our Balsam-poplar, a Sassafras and the analogues of our Per- 
sea and Benzoin, a Catalpa, Magnolias, and a Liriodendron, 
Maples answering to ours, and also a Negundo, and such pe- 
culiarly American Leguminous genera as the Locust, Honey 
Locust, and Gymnocladus. To understand how Europe came 
to lose these elements of her flora, and Atlantic North Amer- 
ica to retain them, we must recall the poverty of Europe in 
native forest trees, to which I have already alluded. <A few 
years ago, in an article on this subject, I drew up a sketch of 
the relative richness of Europe, Atlantic North America, 
Pacific North America, and the eastern side of temperate Asia 
in genera and species of forest trees! In that sketch, as I 
am now convinced, the European forest elements were some- 
what underrated. I allowed only thirty-three genera and 
eighty-five species, while to our Atlantic American forest were 
assigned sixty-six genera and one hundred and fifty-five 
species. I find from Nyman’s Conspectus that there are trees 
on the southern and eastern borders of Europe whieh I had 
omitted ; that there are good species which I had reckoned as 
synonyms, and some that may rise to arboreal height which I 
had counted as shrubs. But on the other hand and for the 
present purpose it may be rejoined that the list contained 
several trees, of as many genera, which were probably carried 
from Asia into Europe by the hand of man. On Nyman’s 
authority I may put into this category Cercis Siliquastrum, 
Ceratonia Siliqua, Diospyros Lotus, Styrax officinalis, the 
Olive, and even the Walnut, the Chestnut, and the Cypress. 
However this may be, it seems clear that the native forest 
flora of Europe is exceptionally poor, and that it has lost 
many species and types which once belonged to it. We must 
suppose that the herbaceous flora has suffered in the same 
1 American Journal of Science and Arts, 3 ser., xvi. 85. 
