Hill: Penobscot Vegetation 311 



two limestone members of the Rockland Formation, one is 

 silicious and the other yields little or no basic soil, since it 

 is highly crystalline, virtually a marble, and so decomposes 

 with difficulty. Most of the other rocks of the area are also 

 acidic, although locally small amounts of diabase, diorite, 

 gabbro and serpentine may be found. 



The climate of the region is that of any moist north tem- 

 perate area with warm days and cool nights during the sum- 

 mer. The proximity of the ocean brings about much more 

 equable conditions than are found inland, and this has a 

 pronounced effect upon the vegetation in that the growing 

 season is prolonged. Data from three U. S. Weather Bu- 

 reau stations on the Maine coast (Eastport, Bar Harbor, 

 Portland) for the ten years 1909-1919 show an average 

 growing season of 166 days; while a similar average for in- 

 land stations (Orono, Millinocket, Greenville) is only 114 

 days. The prevalence of fogs renders the region excessive- 

 lv moist, with a consequent lowering of the temperature. 



Previous Botanical Work 



Although the island of Mount Desert on the eastern bor- 

 der of the Bay, and several areas to the westward, have been 

 carefully studied botanically, the Penobscot Bay region of 

 the Maine coast has been much neglected. Until recently 

 the only work done has been of a desultory nature and en- 

 tirely from the floristic point of view. In 1919 the author 

 (15) published an account of the flora of a portion of the 

 eastern part of the region, to which the reader is referred 

 for references to any earlier works, but no ecological study 

 of the vegetation has been attempted until the present time. 



Acknowledgments 



I wish at this time to express my great indebtedness to 

 Professor George E. Nichols, who has been ever ready with 

 advice and suggestions regarding the work ; and to Dr. John 



