34 
these beds Dr. Britton, Mr. Hollick and Mr. I. H. Woolson have 
obtained many hundred specimens which are permanent and are 
satisfactory objects of study. These I have lately had under 
consideration, have had most of them carefully drawn, and of 
these drawings have composed about fifty quarto plates, some of 
which I now have the pleasure of exhibiting. This material 
gives the first satisfactory view of the flora which it represents, 
and enables me to make this contribution to a knowledge of the 
vegetation, that flourished in the region about the mouth of the 
Hudson, in the Cretaceous age. 
It will, of course, be a long time before a full description of 
this flora can be given, but the hundred species of ferns and ar- 
borescent plants now before us may probably be regarded as a 
fair sample of it; and as a flora of similar botanical character has 
been exhumed from rocks of about the same geological age in the 
interior of this continent, in Greenland and in Germany, we may 
_ infer that this group of plants fairly represents the vegetation of 
the temperate zone in the Northern Hemisphere at the middle of 
the Cretaceous age. 
As is known to most botanists and geologists, a great change in 
the plantlife of the globe took place at the close of the palzeozoicages. 
Then the coal flora, consisting of acrogens with some gymnosperms 
—lycopods, equiseta, and ferns with conifers—gave place to what 
is known as the mesozoic flora, which consisted mainly of cycads, 
conifers and ferns ; the cycads predominating and giving a special 
aspect to the vegetation. In the Triassic and the Jurassaic ages, 
and through the first epoch of the Cretaceous age, this flora ap- 
parently flourished over the whole world. Toward the middle 
of the Cretaceous age angiosperms began to appear and soon 
became the prevailing style of vegetation; this has continued, 
with many changes of degree but little of kind, to the present day. 
The beginnings of the angiospermous flora have apparently 
been found in the Kome beds of Greenland and in the Potomac 
group of Virginia, of which the flora is now being studied by 
Prof. W. M. Fontaine. Here a few angiosperms are found min- 
gled with an abundant flora of cycads, conifers and ferns, but as 
yet without any discovered transitional forms between these 
botanical groups. 
