222 THE GENESIS AND MIGRATIONS OF PLANTS 



from what it is at present — are remains of very frail and deli- 

 cate plants which still live. I have shown that in these clays 

 there exist, side by side, the Sensitive Fern, Onoclea sensibilis, 

 and one of the delicate rock ferns, Davallia tenuifolia?- The 

 first is still very abundant all over North America. The second 

 has ceased to exist in North America, but still survives in the 

 valleys of the Himalayas. These two little plants, once prob- 

 ably very widely diffused over the northern hemisphere, have 

 continued to exist through the millenniums separating the 

 Cretaceous from the present time, and in which the greater 

 part of our continent was again and again under the sea, in 

 which great mountain chains have been rolled up and sculptured 

 into their present forms, and in which giant forms, both of 

 animal and plant life, have begun, culminated and passed 

 away. Truly God hath chosen the weak things of the world to 

 confound those that are strong. 



Other plants equally illustrate the decadence of important 

 types of vegetable life. In the beautiful family of the Magnolias 

 there exists in America a most remarkable and elegant tree, 

 whose trunk attains sometimes a diameter of 7 feet and a 

 height of 80 or 90 feet. Its broad deep green leaves are 

 singularly truncate at the end, as if artificially cut off, and in 

 spring it puts forth a wealth of large and brilliant orange and 

 yellow flowers, from which it obtains the name of Tulip tree. 

 It is the Liriodendron tulipifera of botanists, and the sole 

 species of its genus. This Tulip tree has a history. All 

 through the Tertiary beds we find leaves referable to the genus, 

 and belonging not to one species only, but to several, and as 

 we go back into the Cretaceous, the species seem to become 

 more numerous. Many of them have smaller leaves than the 

 modern species, others larger, and some have forms even more 

 quaint than that of the existing Tulip tree. The oldest that I 

 have seen in Canada is one from the Upper Cretaceous of 

 ^ Report on 49th Parallel, 1875. 



