A ilonograph of the Genixs Alarit. (J7 



Wo know very little of the algal floras of the Siberian Sea 

 and the American Arctic Sea. How many species of Alaria may 

 be found in the regions and in w^hat state of growth they may 

 flourish, is not satisfactorily reported. There are reasons, however, 

 to assume that we may not expect many species from there. Yet 

 the supposition that the north circumpolar regions might have 

 been or may be the center of distribution of Alaria has some 

 probability. 



Starting from the above assumption I venture to say : — Alaria 

 had its origin in the North Circumpolar Sea and migrated south- 

 wards into the Pacific and the Atlantic Oceans as far as where 

 the Arctic currents terminate ; the initial form gradually diverged 

 into the various present species wdiich flourish in a most vigorous 

 state about the southern limits of the Arctic currents. 



In general, the formation in which Alaria plants are habitually 

 found is the sublittoral. They prefer the exposed coasts of steep 

 rocks. Very frequently they form a narrow belt fringing the low 

 water mark or within a few feet below it. Usually, however, 

 they are associated with other algae, almost invariably with other 

 Laminariaceous members, and may thrive to a depth of 4-5 

 fathoms below the low water mark. 



The sporelings of Alaria germinate, except in the extreme 

 north, in early spring. They are found in great abundance on 

 rocks, mussels, larger algae, etc., immediately below the low^ water 

 mark. A few months later, during the spring tide just following 

 the vernal equinox, the w^ater ebbs so as to exposo these sporelings 

 and young shoots to the strong heat of the sun. The majority are 

 destroyed on this occasion, though many other plants adapted to 

 such conditions may survive well. This is undoubtedly the cause 

 why Alaria plants are found at a certain depth below the ordinary 



