152 



DISCOVERY 



Antarctic and Arctic Contrasts 



The contrasts between Antarctic and Arctic land 

 floras are very notable and demand explanation.' 

 The extent of insolation is of course the same in corre- 

 sponding latitudes in northern and southern hemi- 

 spheres. The annual snowfall in the south is probably 

 not greater than in the north, and the wniter tem- 

 peratures, at least in certain parts of Antarctic regions. 

 are not more severe than in parts of Arctic regions. 

 The real explanation is to be found in the short summer 

 with its remarkably low temperatures. Thus in Vic- 

 toria Land in about lat. 78° S. the mean of the warmest 

 month of the year is only 25° F. ; at Cape Adare in 

 lat. 71° 18' S. it is 31-5° F. ; at Snow Hill, Graham Land, 

 in lat. 64° 24' S. it is 30-4° F. ; and at the South 

 Orkneys m about 61° S. it is 32-9° F. Thus there is 

 practically no month in the Antarctic with a mean 

 temperature above freezing-point, while the mean of 

 the three summer months, December, January, and 

 February, is everywhere below 32° F. In Arctic 

 regions summer is warmer and longer. The mean 

 summer temperature (June, July, and August) in on 



Spitsbergen is over 37° F., and the mean of the warmest 

 month, July, is over 40° F. In Franz Josef Land in 

 lat. 80° N. the July mean is 35° F. In other words, 

 the Arctic summer has a mean well above freezing- 

 point. 



This lack of a real summer influences Antarctic plant 

 life in two ways. The winter snow lies late on the 

 ground, and December is generally well advanced 

 before most of the vegetation is laid bare and exposed 

 to sunlight. By early February snow again begins to 

 accumulate, and it may cover the ground throughout 

 the so-called summer. There are only some four to 

 six weeks during which the vegetation, except lichens 

 on cliff faces, is likely to be exposed to the sunlight, 

 and the probability is that the ground has a tempera- 

 ture not above freezing-point even if it is not saturated 

 with ice-cold water ; often it thaws only for a few 

 hours on cloudless days when the sun is strong. These 

 influences are detrimental enough to plant life, but the 

 impossibility of completing the cycle of life-functions 

 in the short cold summer causes the virtual absence 

 of flowering plants. A plant would be unlikely to 

 reach the flowering stage and would have no chance 

 of maturing its fruit. Even Arctic plants in their 

 more favoured circumstances rarely ripen their seeds 

 and frequently reproduce vegetatively. With an 

 average of eight to ten weeks, when the ground at 

 low elevation is free from snow, Arctic plants have to 

 " rush " their life-cycle, flowering frequently before 

 the snow is off the ground, and even then finding the 



summer too short. Antarctic conditions, with low 

 temperatures and the uncertainty of even four weeks 

 clear of snow, deny even this possibility. 



Winter temperatures fall very low, but there is no 

 reason to suppose that a mean of -30° F. is any more 

 prejudicial to plant life than a mean of zero. Through- 

 out the Antarctic w'inter all temperatures are uniformly 

 low enough to give all mosses the hardness of rock. 



These probably are the main reasons of the poverty 

 of the Antarctic flora, but there are contributory 

 factors. The chief sites for plant growth are the 

 islands, particularly small ones, and the rocky coasts. 

 In such places high winds help to keep the surface 

 clear of snow, but these high winds, not infrequently 

 dry and generally cold, are themselves detrimental 

 to plant growth. Nothing could be more hostile than 

 the strong southerly and south-easteily winds blowing 

 from the high-pressure system over Antarctica. The 

 lack of soil has been suggested as an adverse influence. 

 This is doubtful if one considers the habitat of many 

 Arctic plants which, for example, in Spitsbergen 

 maintain a hold on raised beaches, moraines, and even 

 rock faces. In places the level plain of the 



' See article on "Greenland's Plant 

 Seward, Discovery, September 1922. 



Life," by Prof. A. C. 



Antarctic provides 6 to 8 inches of soil, often well 

 impregnated with bird guano, which might furnish 

 suitable sites for the flowering plants. The Antarctic, 

 however, has one influence hostile to plant life that is 

 absent in the Arctic. In summer myriads of penguins 

 haunt the islands and coasts of Antarctica, occupying 

 all the low-lying sites that are first to lose their snow, 

 that is to say, exactly the best sites for plant growthj 

 In the proportion of one per square yard the 

 penguins cover every available site ; nothing escapes 

 their insatiable curiosity or fails to be attractive to 

 their beaks. No plant that had gained a footing 

 would stand the smallest chance of surviving. It is 

 not imreasonable to regard the penguin as one of the 

 agencies hostUe to plant growth in the Antarctic. 



The Origin of Antarctic Flora 



The origin of the Antarctic flora presents a fascinating 

 problem. How did these species of plants reach 

 Antarctica ? It would occupy too much space to 

 analyse in detail the distribution of every Antarctic 

 species, but it may be noted that certain elements are 

 conspicuous. There are the endemic element, which 

 is high in the case of mosses and lichens ; the Arctic 

 element ; and the Fuegian element. The high pro- 

 portion of endemic species can well be explained by 

 long isolation and peculiar conditions of environment. 

 The Arctic element is not easy to explain. Two 

 suggestions have been made. Carriage of spores and 

 soredia in the feet and plumage of birds which wander 

 through 150° of latitude may account for some species. 

 Wilson's petrel and the Arctic tern are birds with this 



