278 Proeeedin<is Port. Soo. Nat. Hist. 



to employ different terms in attempting to classify tliem sat- 

 isfactorily, and this has led to considerable confusion. In 

 the present discussion the term sub-arctic will be employed in 

 referring to such of these plants as occur in the Penobscot 

 Bay region, for no strictly arctic forms are included among 

 them. A more southern element of the boreal flora, on the 

 other hand, is much more definitely marked off and the term 

 Hudsonian is universally used to refer to those species which 

 range to the Labrador Peninsula and Hudson Bay and attain 

 their maximum development in eastern Canada, but which 

 fail to reach the far north. 



The boreal flora as a rule is widespread in northern re- 

 gions, but gradually becomes restricted toward the southern 

 limits of its range, where it occurs only locally in the most 

 favorable situations, such as high mountain tops, sea cliffs 

 or cold bogs. The eastern Penobscot Bay region occupies a 

 midway position, where tlie boreal plants are still fairly 

 widely distributed, but even here certain of the more north- 

 ern species are uniformly restricted to the coastal cliffs and 

 headlands or to bogs. 



St'B-Aectic Plants 



The iTLOst interesting feature from a phytogeogTaphical 

 point of view in the Penobscot Bay region is the occurrence 

 of several species of sub-arctic plants on the cold headlands 

 and sea-cliffs of the outer islands. The extreme exposure of 

 these shores, the constant drenching with cold spray to which 

 they are subjected, and the frequent presence of fogs all com- 

 bine to render conditions quite like those in arctic regions and 

 furnish a halntat where the boreal species can exist. 



The presence of this flora on the eastern Maine coast and 

 in adjacent iSTew Brunswick has long been recognized. As 

 early as 1809 G. F. Matthew published an account of the 



