So8 SECTIONAL TRANSACTIONS.— K. 



to have originated by hybridisation between Group A and S. Aucuparia 

 and S. torminalis respectively. Group A is represented by about half a 

 dozen forms of which some may be pre- or inter-glacial derivatives of 

 S. Aria or allied species, the others being perhaps derived from them by 

 hybridisation. 



Dr. C. G. DoBBS. — The vegetation of Cape Napier, Spitsbergen (10.30). 



Cape Napier is a shingle promontory situated in latitude 78° 39' N., on 

 an innermost branch of Ice Fjord, which penetrates the west coast of West 

 Spitsbergen to a depth of over fifty miles. Behind the main shingle beach 

 lies a small salt marsh and a larger area of pools and bogs, crossed by shingle 

 laterals. The area was described by J. Walton in 1921. 



The object of this investigation has been to record the vegetation in 

 greater detail, and to establish any changes which have occurred during 

 the intervening fifteen years. For this purpose a vegetation map was made, 

 and the frequencies of plants along certain lines were expressed by means 

 of graphs based upon ring sampling. 



Three main associations were found on the small area studied : on the 

 shingle — Dryas fjaeldmark with lichens ; on the tidal mudflats — Cyano- 

 phycece, the grass Puccinellia phryganodes, the moss Swartzia incUnata, and 

 Car ex subspathacea ; in the bog — mosses, Car ex subspathacea and Salix 

 polaris. The succession from bare shingle to fjaeldmark, and bare mudflat 

 to bog, was traced. 



Changes since 1921 were slight, indicating a slow rate of development. 

 Puccinellia, however, had spread some distance by means of broken shoots 

 washed along the tidal channels. Szoartzia and Car ex subspathacea had 

 spread much more slowly on the mudflats, and a pool in the boggy area had 

 become filled with vegetation. 



Mr. A. M. AcocK. — Observations on vegetation and associated soil pheno- 

 mena in Spitsbergen (10.50). 



The severity of environmental conditions in Arctic regions is such that 

 any mitigating influence has a profound effect on vegetation. Small varia- 

 tions in soil characters and micro-relief are reflected in changes in floristic 

 composition and density. 



Apparently associated with the frozen sub-soil and seasonal thawing and 

 freezing of the surface is the peculiar organisation of the soil into the 

 structures known as ' polygons.' A variety of types was observed near 

 Bruce City, Spitsbergen : 



(i) Fissure polygons in silt or clay, 

 (ii) Stone circles with clay centres, 

 (iii) Polygons in stony material, 

 (iv) Elongated forms on slopes. 



A number of mechanisms of formation has been suggested by various 

 workers. The botanical interest centres in the rearrangement of the 

 mechanical contituents of the soil and in local differences in exposure, 

 duration of snow lie, and moisture, as a result of doming of the polygon 

 centres. There is generally a concentration of vegetation on the margins- 

 of polygons, either rooted between stones or in humus - filled fissures 

 between polygons. 



