262 



THE GEOLOGIST. 



EoYAL Institution.— Jf«rc/i 7. — " On the Distribution of Ifortliera 

 Plants." By Professor D. Oliver. The discourse referred primarily to 

 the botanical evidence bearing upon the hypothesis advanced by Pro- 

 fessors linger* and Heerf of an Atlantic communication between Europe 

 and America at some period of the Tertiary epoch. The close analogy 

 which is to be traced between the Miocene Flora of Central Europe and the 

 existing Flora of the Eastern American States, these authors conceive can 

 only be explained by assuming such direct overland connection of the two 

 Continents. 



The speaker explained the basis upon which comparisons between two 

 recent floras and between a recent and a fossil flora should rest, referring 

 to the peculiar conditions which affect the latter comparison owing to the 

 imperfect and partial character of the fossil element. The general cha- 

 racter of the Tertiary Flora of Central Europe was described. In the 

 Tertiary beds of Switzerland, according to Professor HeerJ about 800 

 species of Phanerogamia have been discovered, referable to 197 genera 

 (exclusive of Fhyllites, Carpolithes, etc.), of which number 154 still exist. 

 Of these genera — 



76 are common to the Swiss Tertiary, 



and to the present flora of . . Europe. 



77 Japan. 



88 ...... . Ditto, States, America. 



120 . Europe and Asia (taken toge- 



ther, and inchiding Japan). 



It is to be noted that the 77 of Japan include 26 not occurring in 

 Europe : amongst them several forms highly characteristic of the Tertiary, 

 as Glyptostrohiis, numerous Fici, coriaceous-leaved oaks and Lauracece, 

 JuglandecB, Jjiqiiidamhar, etc. 



The genera, common to the Swiss Tertiary and the Uuited States, which 

 are not found also in the Old World are Sahal, Taxodium, BiimeUa, Lirio- 

 dend^ron, Ceanot/ius, Ptelea, and Carya. But in respect to these 7 it was 

 observed that at least 5 were very doubtful determinations. The 9 largest 

 orders of the ' Flora Tertiaria Helvetise ' are Legwminosce, Amentacece, 

 CyperacecB, Proteaceae, Lauracece, GraminecB, Coniferoe, Comjpositce, and 

 AceracecB. Of these Orders 3 are included in the 9 largest of Europe, 4 

 in the 9 largest of the United States, and 6 in the 9 largest of Japan, 

 while the remaining 3 of the Tertiary, not included in the 9 largest 

 orders of Japan, are much more largely developed in Japan than in 

 the United States. They are Pauracece, Aceracecs, and Proteacece. 



The proportion of ligneous to herbaceous species in the above floras 

 was alluded to. Heer estimates ligneous plants to have formed about 66 

 ])or cent, of the Phanerogamic vegetation of the Tertiary in Switzerland. 

 The speaker considered this estimate as too high, believing that sufficient 

 alloAA ancc had not been made for the advantages that ligneous plants, 

 which are often tall-stemmed, possess over herbaceous species in securing 

 access of tlieir leaves and debris to the waters in which they had been 

 iloated, and ulliniately preserved. He admitted, however, that ligneous 

 species ^^ ere relatively very numerous in the vegetation of the Tertiary 

 ])eriod. The proportion of hgneous plants he estimates in the existing 

 flora of Japan at near 10 per cent., in the Southern States 22, JSTortherii 

 States 18, Europe 9 to 12. 



* 'Die yersimkcne lusel Atlantis.' f 'Flora Tertiaria Helvetite.' 



t The Tertiary ilala were throughout derived from the 'Flora Tertiaria llelvetire ' of 

 Professor Ilci r. 



