32 MASSACHUSETTS HORTICULTURAL SOCIETY 



of peat lands and their agricultural and industrial possibilities, is 

 readily apparent. 



The role of vegetation in the conversion into peat lands of water 

 basins or of wet depressions on uplands, along rivers, or at the coast 

 has long been recognized, but the sequence of plant associations 

 forming peat, the possible retrogressions, the origin and the condi- 

 tions giving rise especially to ericaceous heath-bogs, and lastly the 

 manner in which peat accumulation takes place are still problems 

 at present under much discussion by investigators. 



The general conclusions formed from one point of view lead, 

 briefly stated, to the following: In common with other glaciated 

 regions the origin of the modern era of plant life in Massachusetts 

 dates back to the period when the continental glaciers receded 

 toward the North pole and vegetation from the south and west once 

 more migrated northward in the wake of the retreating ice sheet. 

 During the time that has elapsed since the recession of the ice front, 

 variously estimated at from 30,000 years for southern states to 

 20,000 years or less for northern states, many plant societies have 

 doubtless occupied this region, which at the present time are char- 

 acteristic of regions farther north. Thus the first vegetation to 

 seize upon the areas which became exposed gradually may have 

 been quite similar to the tundra of the far north, extensive, 

 compact mats of herbaceous plants, and woody, prostrate forms, 

 shrubby in appearance and chiefly of the ericaceous family. Fol- 

 lowing the tundra there developed slowly, it is presumed, a type of 

 bog shrub stage and later one of temporary climax vegetation simi- 

 lar to the spruce and fir forests, which still comprise an important 

 element on the peat lands of northern Massachusetts. Last of all 

 followed in their northward march components from the southern 

 coastal district, and from the plateau regions the deciduous and 

 hardwood trees and their dependents, which at the present time 

 predominate on the peat lands of such states as Ohio and Indiana. 



Deciduous trees and some of the plants associated with them 

 have now, that is within very recent geological time, regained only 

 a position of their original home; they have commenced to invade 

 this region and are establishing themselves in the more favorable 

 sites, thus giving rise to a mixture of coniferous and deciduous 

 forest type of peat lands, transforming them into a new and differ- 



