34 



these beds 1 )i'. Britton, Mr. 1 lollick aiul Mr. I. II. Woolson have 

 obtained many hiiiidred .s[)eeiineiis which are permanent anil are 

 .satisfactory objects of ftudy. Tliese I have lately had under 

 consideration, iiave had most of them carefully drawn, and of 

 these drawiny^s have composed about fifty quarto plates, some of 

 which I now have the i)leasurc 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 plantlifeofthe globetook place atthecloseofthepalaeozoicages. 

 Then the coal flora, consisting of acrogens with some gymnosperms 

 — lycopods, equiseta, and ferns with conifers — gave place to what 

 is known as the viesozoic 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. 



