124 Rhodora [May 
THE PLANT-FORMATIONS OF EASTERN 
MASSACHUSETTS. 
J. W. BLANKINSHIP. 
Tuis paper is the result of studies on the eastern coast of Massa- 
chusetts and includes in general the region from Cape Ann to Plym- 
outh and from Cape Cod to some 15 miles west of Boston. In the 
north this region is mainly broken and hilly, but southward spreads 
out into extensive sandy plains. It is bounded on the east by the 
sea with its extensive salt marshes and there are innumerable ponds 
and slow-flowing streams which support a characteristic vegetation, 
while the Blue Hills some 600 feet high are the most prominent land- 
mark. Almost the whole region is sparsely wooded (about half with 
conifers), and much of it is covered with glacial drift. The numer- 
ous hills have usually their tops and upper slopes well denuded of 
soil and sparse of vegetation, and these hilltop barrens often support 
characteristic species. The bogs of the North here approach their 
southern limits and bring with them their own northern species. 
Withal, this debatable ground between the Carolinian and Canadian 
regions — often misnamed the Transitional Zone, possessing a flora 
made up of the mingling of the species of two very different regions 
and rich with intergrading forms, is one well worthy of study from 
the ecological as well as the systematic standpoint and these brief 
notes are offered more as an aid to others interested in its ecology 
than as a study complete in itself. 
The range or area over which a given species may be naturally 
distributed is determined by latitude, altitude, humidity and geo- 
graphical barriers, which serve to group species into “floras,” each 
occupying an essentially distinct biological area. In each of these 
biological regions the flora comprises a number of segregated groups 
of plants occupying different areas called “ habitats," each composed 
of essentially different species adapted to this particular combination 
of physical, chemical and biological conditions. ‘The efficient factors 
of these plant-habitats are the chemical nature of the soil with its 
physical condition, the amount of contained water, the relative 
amount of sunlight and the effect of biological agents, somewhat 
modified by variation in temperature, exposure and proportion of 
humus present in the soil. The total aggregation of species usually 
