62 



confident of this from acrobiological 

 studies recently pursued to the highest 

 latitudes where a considerable range of 

 such microscopic airborne particles is 

 often to be found, some at least being 

 in a viable condition. 



PLANT PHYSIOLOGY 



Let us dwell for a moment on this 

 last important discipline, physiology. 

 There is a great need for far more plant 

 ph^•siological work in the Arctic, where 

 the extreme conditions often offer at- 

 tractive possibilities, but relativelv lit- 

 tle has yet been attempted, some lines 

 have been entirely neglected so far. 



Plant growth rates in the Arctic are 

 generally reduced far below those typ- 

 ical of temperate regions— possibly ow- 

 ing in part to the slowness of protein 

 synthesis as well as to reduced cell 

 elongation at low temperatures. Also, 

 growth is subject to unusually great de- 

 pression by locally unfavorable condi- 

 tions of soil or climate in the Arctic. 

 The low growth-rates result in an ac- 

 cumulation of sugars and probably also 

 of soluble nitrogenous compounds, and, 

 in turn, the high sugar levels are sup- 

 posedly responsible for some of the low 

 rates of assimilation which have been 

 obser\'ed. On the other hand, conver- 

 sion into anthoc\anins may possibly 

 lead in the opposite direction, and their 

 prevalence in the Arctic may effect an 

 increase in the absorption of radiant 

 energy and, conceivably, result in 

 higher rates of transpiration and metab- 

 olism. It is certain that in the Arctic, 

 given suitable conditions of light and 

 temperature, which rarely persist there 

 for long, photosynthesis may be rapid. 

 However, transpiration appears in gen- 

 eral to be rather feeble. 



Photosynthesis has, however, been 

 shown in some plants to proceed 

 throughout the twenty-four hour arctic 

 day; and it may be recalled that bac- 

 terial activity is now known to con- 



PHYTOGEOGRAPIIY AND EXPLORATION 



tinue at temperatures down to at least 

 7°C., while there are claims of algal 

 activit}' in brine down to — 15°C. 



There is some evidence of a lack of 

 available combined nitrogen in most 

 arctic land habitats, owing perhaps to 

 the low activity of soil microorganisms, 

 but this question requires detailed in- 

 vestigation. Also pregnant with possi- 

 bilities of explanation of plant ranges 

 would be an investigation of the photo- 

 periodic and night-temperature re- 

 sponses of arctic plants— such as have 

 recently been discovered to be of great 

 importance farther south. 



PHYTOGEOGRAPHY 



Before concluding I should like 

 to return to phytogeography for two 

 special items, the first of which is in- 

 triguing rather than important. In 

 1937 I found, growing around Old 

 Norse ruins in southwestern Green- 

 land, the descendants of plants which 

 had almost certainly been introduced 

 by the Vikings from continental North 

 America. The known but restricted 

 ranges of these plants, in some cases 

 barely overlapping on the American 

 Atlantic seaboard, give strong sugges- 

 tions as to where they originated. 

 Their detailed study should tell us 

 where to search for the ruins— the only 

 evidence which the more cautious 

 archaeologists, who are unconvinced 

 by all earlier claims, will accept as the 

 final corroboration of ancient sages 

 (and current belief) that these shores 

 were known to European civilization 

 centuries before the time of Columbus. 



The other item of phytogeography 

 concerns the persistence of plants on 

 ice-free areas of the North. Having 

 practically witnessed the colonization 

 of plants on recently bared tracts in 

 various parts of the Arctic, and mar- 

 velled at the luxuriant vegetation that 

 in some places may now be seen grow- 

 ing alongside or actually over ice, I 



