370 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



EQUISETUMS AND CALAMITES. 



Dr. M'Nab traces a closer resemblance between the exist- 

 ing equisetums (" horse-tails ") and the fossil calamites of the 

 coal period than has hitherto been recognized. A comparison 

 of the habit of growth and of the microscopical structure of 

 both leads to the conclusion that the difference is but small. 

 Both have the same large under-ground stem, running for a 

 considerable distance, branching, and giving off aerial shoots 

 of short duration, mostly annual in equisetum, and probably 

 not more persistent in tlie calamite. The cone-like fruit is 

 in both terminal upon these erect cylindrical shoots. The 

 widest difference is jDrobably in the arrangement of the parts 

 of these cones, the equisetum having all the leaves of the fruit 

 modified, and bearing spore cases ; the calamite having only 

 the alternate whorls as modified. The character and arrange- 

 ment of the various tissues in the two appear to be closely 

 similar. Trimet'C s Jour. JBot.^ March^ 1873, 79. 



ANCIENT VEGETATION IN ENGLAND. 



Mr. Thistleton Dyer, in a review of Syme's English Botany^ 

 calls attention to the fact that at the close of the pliocene 

 period N^orthern Europe, including the greater portion of the 

 British Isles (which were then connected with the Continent), 

 was covered with a continuous sheet of ice, which entirely 

 exterminated any vegetation that might have previously ex- 

 isted there. The surface of the islands, therefore, appears to 

 have been a tabula rasa in the entire absence of vegetation. 

 As the surface gradually rose above the ice and Avater it be- 

 came slowly stocked with life from the Continent, with which, 

 as stated, it Avas joined. 



The climate, Avhich had been milder during .the period of 

 submersion, became again cold ; the mountains were once 

 more clothed with glaciers, though less extensive than before. 

 The first vegetation introduced must have been of an arctic 

 character, this giving way as the climate ameliorated, and 

 new plants pressed forward from the South. 



Of this ancient vegetation there are still remains on the 

 summits of the mountains and elsewhere, such as the Scotcli 

 fir [Pinus sylvestris), found also in the bogs of Ireland and 

 at tiie bottom of those in Denmark. Subsequently the beech 



