94 



In the light of these observations it clearly follows that while 

 practically all of the species which at present comprise the flora 

 of this state have been derived directly from the south, never- 

 theless many of them — certainly those which today are common 

 to Europe — must have existed in preglacial times not only here 

 but far to the north. Of the forms which are now endemic to 

 North America many, like the tulip tree, sweet gum, and sassa- 

 fras, are known to have been native to Europe in preglacial time, 

 their extinction there being accounted for by assuming that 

 they were trapped, as it were, between the advancing glaciers 

 toward the north and insurmountable east-west mountain ranges 

 toward the south and thus wiped out of existence. But it is 

 equally certain that a large share of these endemic species have 

 never occurred in Europe, and for such species there are two 

 alternative possibilities: either they must have attained their 

 present evolutionary development since the discontinuance of 

 the circumpolar land bridge, or else they must have been re- 

 stricted until within comparatively recent times to the warmer 

 parts of this continent, so that the opportunity to migrate into 

 Europe has never been afforded them. 



The present distribution of the vegetation within the state is 

 the effect of a complex of causes, some of which have long since 

 ceased to operate while others are still active. To a large extent 

 coeval factors of topography, soil, and climate seem ample to 

 explain the observed relations. But there is one problem of 

 plant distribution for which coexistent forces fail to offer any 

 satisfactory solution. This problem relates to the segregation 

 in the southeastern part of Connecticut of a remarkable group 

 of plants which are characteristic of the Atlantic coastal plain 

 region from Long Island and New Jersey southward.^ The 

 majority of the species involved also range eastward into Rhode 

 Island and southeastern Massachusetts, some of them following 



' In order, however, to avoid any misapprehension it should be remarked that 

 very many coastal plain plants are more or less widely distributed through the 

 state. A comparison, for example, of the Connecticut catalogue of ferns and flower- 

 ing plants with Stone's Plants of southern New Jersey (Ann. Rept. N. Jersey State 

 Mus., 1910) shows that nearly 75 per cent of the 540 species listed as characteristic 

 of the New Jersey coastal plain are also found in this state. 



