910 THE EXTINCTION OF SPECIES. 



periods. The oceun-enee of these curious Calamites of the Carboniferous period 

 strikes one most when they are found in localities where the ground is now occupied 

 by low herbs, Mosses, and Lichens, and is covered with snow for three-quarters of 

 each year, as is the case in Nova Zembla, Spitzbergen, and Bear Island. In the 

 region of the Alps, too, we encounter spots where this surprising phenomenon is 

 again presented. One of the most remarkable is the upland valley in the TjtoI 

 known as the Gschnitzthal. I have for many years passed the summer months in 

 that valley, and it is there that the greater part of this Natural History of Plants 

 has been written. The house which I occupy stands at an elevation of 1215 metres 

 above the sea-level, and is built upon a diluvial moraine in the middle of the valley. 

 The glaciers which made the moraine have retreated 15 kilometres, and now form 

 the head of the valley. On its debris, dating from the Diluvial period, now grow 

 Firs and Pines, Junipers and Heather, all of which are members of the Baltic Flora 

 Six hundred metres higher up, arboreal growth ceases and the sides and shoulders 

 of the mountains are clothed alternately with extensive Alpine meadows and scrubs 

 of Alpine Rhododendrons and carpets composed of Azalea prociimbens and of creeping 

 Dwarf Willows. On the Steinacherjoch, one of the neighbouring ridges, at an 

 elevation of 2200 metres above the sea-level, the gi-oimd consists of dark fissui-ed 

 slabs of schist, covered with Lichens and Mosses, and here and there overgrown also 

 by Saxifrages and Primulas. If one of these slabs be split open, the inside is found 

 to bear the impress of Calamites and giant Ferns of the Carboniferous period. 

 What an endless series of changes must the vegetation have tmdergone since the 

 time when groves of Calamites flourished here. Over and over again has the place 

 wherein they now repose been turned into the bed of a sea wherein were constructed 

 the coral reefs which now surmount the dark ancient schist in the form of pale grey 

 dolomitic peaks. Forest after forest of Coniferous or of Angiospermous trees has 

 spread its shade over the spot for a time and then passed away. Huge tracts of 

 ice have filled the entire valley, and upon the debris of the moraines deposited by the 

 glaciers in their progress now rests a carpet of Primulas, Saxifrages, and Gentians. 



" Ebbe und Flut — so wechselt der Tod und das bliihende Leben, 

 Blumen pflauzet die Zeit auf das vergessene Grab." 



