272 ESS A YS. 



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 Cotton woods 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. 1 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 which 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 Siliquastritm, 

 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. 



