BLOCK ISLAND. 67 



The flora is morainal in its general character, except in the peat 

 bogs and on the limited sand-dune and sea-beach areas, and has 

 its nearest analogue in that of Montauk Point\ In fact, if we 

 could imagine Montank Point to be despoiled of its few remain- 

 ing trees and converted into an island it would bear a striking 

 resemblance, geologically and botanically, to Block Island. 



Causes Which Have Determined and Mocified the Flora. 



In discussing the causes which have determined the location 

 of any flora and subsequently modified its characters, two 

 prominent factors nearly always have to be considered — the 

 geological and the human. Each of these may have been in- 

 strumental in both introducing and eliminating certain species, 

 and the discussion of a flora cannot be considered as complete 

 unless they are taken into consideration. The influence of man 

 is usually so obvious as to appeal at once to any observer or 

 else it is a matter of more or less definite record. The geo- 

 logical influence however is often so obscure and has its begin- 

 ning at such a remote period that it usually escapes attention. 

 In its widest application this includes atmospheric and ocean 

 currents, soil, climatic changes, changes of level, etc. 



From a study of the existing geological and floral conditions, 

 as I have elsewhere attempted to demonstrate,- the indications 

 are that at the close of the Ice Age there was a continuous strip 

 of land, except for certain ri\er outlets, extending from what is 

 now New Jersey to the southeastern New England coast, with a 

 large body of fresh water occupying the deepest parts of w^hat is 

 now the basin of Long Island Sound. This strip consisted of 

 an elevated portion along the northern border, formed by the 

 terminal moraine, left behind on the final retreat of the ice, and 

 a plain region to the south, of varying width, representing what 

 remained of the old Tertiary coastal plain, which formerly ex- 

 tended out to what is now the lOO-fathom contour. The flora 

 which had been driven southward b}^ the invasion of the ice re- 



iSee "A trip to Montauk Point." Arthur Rollick, Bull. Torrey Bot. Club, 

 xviii. (August, 1891), 255, 256. 



2 See " Plant Distribution as a Factor in the Interpretation of Geological Phenom- 

 ena," etc. Trans. N. Y. Acad. Sci., xii (1893), 189-202. 



