l6] VEGETATIONAL TYPES OF SEAS 537 



Agarum as well as of Laminaria abounding, associated with Red 

 Algae such as species of Lithothamnium and Lithophyllum, and often 

 beset with epiphytes. Even on desolate Akpatok Island in Ungava 

 Bay the present writer has measured specimens of Laminaria longi- 

 cruris up to 47 feet (14-3 metres) in length, and doubtless longer 

 ones occur in the great off-shore beds. Such luxuriant algal vege- 

 tation which survives the arctic ice may almost be compared with 

 the Pacific Macrocystis that ranges nearly to the tropics. Although 

 the lower limit of the photic region is often placed at only about 

 36-40 metres in the Arctic, even oflF far northern Spitsbergen Deles- 

 seria simiosa has been dredged ' quite fresh ' from as deep down as 

 155 metres and Ptilota pectinata has been brought up from a re- 

 ported 274 metres. Presumably these were detached specimens ; 

 but it may be noted that vegetation of Phycodrys and Pantoneura has 

 been reported from depths down to 118 metres off the indubitably 

 arctic Jan Mayen Island. 



The periodicity of arctic Algae appears to be much like that of 

 cool-temperate ones, and indeed many species are common to both 

 regions. However, in conformity with the virtual absence of annuals 

 among the higher plants on most areas of arctic land, none at least 

 of the more massive types of Algae is supposed to be able to complete 

 its cycle of development in less than a year in the Arctic. Also in 

 conformity with the situation in cool-temperate seas, it seems that 

 vegetative activity prevails in summer and reproductive activity in 

 winter for types growing well below low-tide mark, even though the 

 temperature is commonly from —1° to —2° C. during the latter 

 season when darkness largely prevails. Indeed it has been claimed 

 that the richest local algal vegetation may occur at depths where the 

 temperature does not rise above 0° C. at any time of the year. 



Owing in part to differences in such conditions as those of tem- 

 perature and salinity, and in part to factors not yet understood, 

 different arctic seas in spite of their connection with one another are 

 apt to possess distinct algal floras, the dominant Laminariales, for 

 example, being often different in Spitsbergen, Siberia, and arctic 

 America. Beyond this, the benthic flora and vegetation tend to be 

 far poorer in waters of low salinity, such as occur near the heads of 

 fiords into which large streams flow, in Hudson Bay, and off the 

 coast of parts of Siberia near the mouths of great rivers, than they 

 are in waters of more normal marine salinity. 



In the Antarctic, again, the vegetation of the eulittoral zone is often 

 very poorly developed because of exposure and ice, which tears plants 



