LINNE.VN SOCIETY OF LONDON. h^ 



Nephroclium ealcaratuin, Hook. 



flaccidiim, Hook. 



Pteris aquiliua, Linn., var. 



marginata, Bori/. 



Ouychiiim auratmn, Kmilf. 



And finally eight species of Phanerogams : — 



WoUastonia sp. 



2 species of Conyza. 



Senecio s]3. 



Scit'vola Koenigii, Vahl. 



Tournefortia argentea, Linn. 



CTyuiiiothrix elegaiis, Bme. 



Phragmites Eoxburgliii, Kees. 



These ])lants from the general snrface of the island, with 

 perhaps a single exception, were grown from small seeds or 

 spores easily carried by the wind. Probably the large number 

 of Forns growing on the barren ash found a soil on wdiich tlie 

 spores could germinate and develop the prothallus in the algal 

 covering of the ash. 



There can be little doubt that in the case of new islands, 

 whether of coral or volcanic origin, the first vegetation is borne 

 to them by water and air currents. 



Returning to our own island, let us see what was its con- 

 dition when the first members of our present Flora made their 

 ap])earance. 



The Tertiary Period had closed. Only in the immediately pre- 

 ceding Upj)er Ci'etaceous rocks had there been any association of 

 species in a Flora analogous to the geographical groups of our 

 own day. The plants that have been discovered in the Eocene 

 beds possess the facies of a tropical flora; the Miocene plants 

 indicate a slight decrease in temperature, and this continues 

 till we reach the subtropical flora of the Pliocene. There then 

 appeared a remarkable change in the climate, and the Pliocene 

 phxnts perished before the advancing boreal cold. The Pliocene 

 plants do not belong to the same genera, seldom even to the 

 irame Orders as the flora which follows; and they could not con- 

 sequently have any ancestral relation to it. The cold that drove 

 before it the subtropical vegetation was the forerunner of the 

 great ice age. Advancing in front of the ice, the first repre- 

 sentatives of our existing flora reached us from the north, where 

 they had not, however, long established themselves, seeing that 

 the Tropical and Subtropical floras of the Tertiary period 

 flourished far within the Arctic Circle. The remains of these 

 earliest members of our present vegetation are buried in the 

 Cromer Forest-bed with the bones of the extinct mammoth, the 

 rhinoceros, the hippopotamus, and the cave-bear, and of tlie still 

 living horse, red deer, beaver, mole, &c. Only in a single case 

 has it been impossible to correlate wliat appear to be empt^ 

 follicles with the corresponding parts of an existing plant ; and it 

 is possible these fruits may represent an extinct species, though 



:/2 



