FIELD AND FOREST. I 23 



be the more southern form of the two, notwithstanding the specific 

 name of the former. Drosera filiformis takes the place of D. rotundi- 

 folia and D. longifolia, and Polygala cruciata, and P. brevifolia the 

 place of P. sanguined and P. paucifolia. 



It is a curious fact that the line which separates the two adjoining 

 flora follows the geological variation. The whole of Cape Cod, (con- 

 sidering this as including Plymouth, which is not originally reckoned 

 as a part of the Cape,) Nantucket and the eastern end of Martha's 

 Vineyard belong geologically to the drift and alluvium formation. 

 The western end of the Vineyard belongs to the miocene tertiary, and 

 is not nearly so distinctive in its flora as the eastern end. 



The temperature of this district is equally marked; and this fact 

 helps to account for the southern character of its flora. Both the heat 

 and cold on the islands and coasts of southeast Massachusetts, are 

 much modified, not being nearly so extreme as a few miles further 

 north. The well-known mildness of Newport, Rhode Island prevails 

 throughout the Cape region. In winter the difference in temperature 

 is especially noticeable. The Gulf stream runs near enough to the 

 coast to produce a sensible effect. Even if that were not the case, the 

 projection of this region so far into the ocean could not fail to cause a 

 modification of temperature. So great is this modification that 

 the mean winter temperature at Nantucket is 7 warmer, and. at New 

 Bedford, nearly 5 ° warmer than at Cambridge, which is about 70 

 miles north of Nantucket, and 50 north of New Bedford. Williams- 

 town in the extreme northwest of Massachusetts, is io° colder than Nan- 

 tucket and 7 colder than New Bedford, for the average of the winter 

 months.* 



In this description no attempt has been made to give a complete 

 list of the flora of this district, but only enough to indicate the charac- 

 ter of the predominant vegetation. The facts cited show that the region 

 there described is the northern limit of a botanical zone which stretches 

 to the southern boundary of Maryland. 



Looking at a still larger field, we may venture to divide the whole 

 Atlantic coast of the United States, into three zones of vegetation, the 

 first running from the Gulf of Mexico to Southern Maryland, the 

 second from that point to Cape Cod, and the third from Cape Cod to 



*I am indebted for these climatological facts to Lorin Blodgett, Esq., author of 

 "Climatology of the United States." 



