78 THE FLORA OF THE AMBOY CLAYS. 
mass of material has been gathered by Lesquereux, Ward, Fontaine, and 
the writer, as a preparation for the work of illustrating the wonderfully 
rich Cretaceous and Tertiary flora of North America. Although but a 
beginning has yet been made, already the remains of at least a thousand 
distinet species of arborescent plants have been brought to light. The 
botanical relations of many, perhaps most of these, are yet to be accu- 
rately determined, but the general character of the vegetation which 
covered our continent in the later geological ages has certainly been 
ascertained, and much light has been thrown on the derivation and 
history of our present flora. 
With the facts before us we are fully warranted in making the state- 
ment that our angiosperm flora began its existence on this continent in 
early Cretaceous times; that even then its present aspects were distinetly 
developed, and subsequent changes have been rather of degree than of 
kind. In the banishment of our Tertiary flora from the great area it 
once oceupied, and its restriction to the narrow space at the south into 
which it was foreed, many of its finest elements were destroyed; and 
when, with an amelioration of climate, the exiles returned to that portion 
of their former home again opened to them, they came as a handful repre- 
senting a host, perhaps as solitary species, remnants of generic groups that 
had mostly perished by the way. 
Among these survivors the Sequoias stand first in magnitude and 
interest, and their story has been admirably told by Dr Gray in his 
Sequoia and its History. Gingko and Platanus have been described by 
Prof. Lester F. Ward in several memoirs. The Liriodendron, the Magnolias, 
the Liquidambar, the Cypress, and the Sassafas will also, I hope, have 
their biographers, and to aid in the task of one of these I ncw give some 
of the facts which have come to my knowledge in regard to the history of 
our lyre-leaved tulip tree. 
At least two species of Liriodendron are indicated by leaves found in 
the Amboy Clays—Middle Cretaceous—of New Jersey, and others have 
been obtained from the Dakota group, from the Upper Cretaceous strata 
of Greenland, and the Laramie of the West. Though differing considerably 
among themselves in size and form, all these have the deep sinus of the 
