ACKNOWLEDGMENT. 



In the foregoing pages, the writer has endeavored to give 

 proper credit to those who have contributed towards extending 

 the size of the flora, or a knowledge of the distribution of the 

 species. But other assistance has been rendered him by per- 

 sons not directly interested in the local character of the work 

 which should not pass without an acknowledgment. He is 

 indebted to Prof. Asa Gray, Prof. G. L. Goodale, and Prof. 

 Sereno Watson of the Cambridge herbarium, for much valuable 

 assistance during the past five years in identifj'ing many dif- 

 ficult species of plants ; to Prof. W. G. Farlow, for many 

 kindnesses in determining the lower cr3'ptogaras ; to Prof. 

 T. P. James, for similar services regarding the mosses ; to 

 Prof, C. S. Sargent, for much information of value concerning 

 the trees and shrubs, and to Mr. Chas. J. Sprague, not only 

 for his contribution of the entire list of lichens, but also for 

 kindly remembering to communicate any rare plant found while 

 collecting in Essex county. 



The writer also desires to express his obligations to Messrs. 

 Edwin and Charles E. Faxon, for their kindness in revising 

 the final proof, and to Mr. Woodbury P. Conant, for his as- 

 sistance in preparing the index. 



12 (177) 



