I 8 ONOCLEA SENSIBILIS. SENSITIVE lERN. 



are known as Evolutionists account for the great variations 

 between living forms and those which existed in the earlier 

 •---eoloo-ic ages. There are other scientific men who regard 

 these differences between the early and recent floras as the result 

 of sudden geologic or cosmic catastrophes, destroying existing 

 forms, and almost contemporaneously succeeding with new 

 ones ; and who believe that if any did not happen to come 

 wholly within the range of these great disturbing influences, 

 there would be no reason why a form might not continue without 

 material change for countless ages. 



These geological discussions have a peculiar interest in con- 

 nection with our present subject, the Sensitive Fern, for its 

 remains are found in some very old geological formations in 

 which vegetable remains exist, and precisely in the form in 

 which we find it now. According to Professor Daw^son, of 

 Montreal, it was in existence near the Cretacean age, or that 

 time in the earth's history when only reptiles crawled over the 

 surface, and the mammalian or sucking animals had not yet 

 appeared. In Dr. Dawson's own language, in his address to 

 the Natural History section of the American Association for 

 the Advancement of Science, delivered at Detroit in 1875, he 

 says: 'Tn a collection of fossil plants from what may be termed 

 beds of transition from the Cretaceous to the Tertiary, I find 

 among other modern species two recent ferns most curiously 

 associated. One is the common Onoclca scnsibilis, found now 

 very widely over North America, and which in the so-called mio- 

 cene times (about the middle of the mammalian era preceding 

 man) lived in Europe also. The other is Davallia tcnnifolia, . . . 

 still abundant on the other side of the Pacific (and Dr. Dawson 

 might have added, still growing with the Onoclca there). These 

 litde ferns are thus probably older than the Rocky Mountains 

 and the Himalayas, and reach back to a tinie when Mesozoic 

 Dinosaurs were becoming exdnct, and the earliest Placental 

 mammals being introduced. Shall we say that these two ferns, 

 and along with them our two species of Hazel and many other 



