72 The Irish Naturalist. 



POSSIBLE ARCTIC PLANT-BEDS IN IRELAND. 



BY JAMES BENNIE, 



Her Majesty's Geological Survey of Scotland. 



It has been suggested to me that a summary of what I have 

 got from Arctic Plant-beds in Scotland, and a description of 

 where and how they occur, might be of advantage to students 

 of nature in Ireland, as to where and how the same things 

 might be got in that country. 



What has been got : — Chiefly arctic plants of six or seven 

 species, the most abundant being leaves of the arctic Willows 

 — Salix herbacea, S. reticulata, S. polaris, Oxyria digynia, 

 Betula ?iana y and Dry as octopctala, and associated with them, 

 the remains of Apus glacialis, a crustacean now only known 

 living in the land-lakes of Spitzbergen and Greenland. Of 

 the arctic Willows the one in greatest abundance was Salix 

 herbacea, which was in thousands upon thousands. 5\ reticulata 

 came next, then S. polaris. Betula nana, though not rare, 

 was comparatively infrequent, while Dryas octopctala was 

 excessively rare, only about half a dozen leaves being got 

 altogether. The Apus remains were comparatively abundant, 

 indicating hundreds of individuals. Besides leaves, seed-cases 

 were abundant. A few leaves of other plants occurred, and 

 seeds of the ordinary water-plants — the pondweeds and the 

 sedges were very numerous. 



Where they occurred : — In the bottom of old silted-up 

 lakes, and generally in thin layers in silt or clay ; sometimes 

 amongst other vegetable debris, and occasionally as single 

 leaves in the silt. These old lake-deposits lie directly or 

 nearly so upon Boulder clay, in the flat spaces or hollows 

 between hillocks or mounds of that glacial drift ; and thereby 

 we get evidence of the date of their existence. It must have 

 been soon after the ice melted from off the land, and water 

 became possible as water, to form pools in the hollows, and 

 plants could grow on the hills or hillocks surrounding them. 

 This date is confirmed by the characters of the Arctic plants, 

 which are such as prove a climate 20 degrees colder than what 

 prevails in the same places at present ; and also by the occur- 

 rence of the Apus, which is now found living only in Green- 

 land and Spitzbergen. 



