and the consequent necessity of beini;: in many places at about the same time, 

 and it can be readily understood that the field work could not be accomplished 

 in one or even two seasons. Indeed, it has required several more than that. 

 Xothinji' but a love of the subject would fortify one with the required patience. 



The necessity of visitins; the trees in their native haunts is evident. This 

 has brought me much in contact with the country folk in remote regions aud 

 has been associated with many novel and generally pleasant experiences. The 

 visit of an " outsider " ofttimes seemed as welcome an occasion to them as the 

 opportunities of their respective localities, and often contact with them, were 

 enjoyed by me, and I gratefully remember many acts of kindness in these 

 hospitable people. 



Occasionally it was my good fortune to have the com])any of fellow botanists 

 in the field and enjoy the benefits of their familiarity with the trees of their 

 respective regions. Such was my experience in studying the interesting trees 

 of Staten Island with Mr. Wm. T. Davis, for whose assistance I am very 

 grateful. 



A rare treat I found in store when I dropped in upon Prof. C. D. Beadle, 

 botanist, at Biltmore, N. C, and enjoyed a few days' sojourn with him working 

 np certain species of the Alleghany Mountains, and to Professor and Mrs. 

 Beadle I am under lasting obligation. 



For able counsel and assistance in many ways I am indebted to my good 

 friend, Prof. Wm. Trelease, director Missouri Botanical Garden. To Dr. X. M. 

 Glatfelter, whose familiarity with the Willows of Missouri was of material 

 assistance to me, I am likewise grateful. So, too, to Mr. G. W. Letterman, with 

 whom I made several visits to the valley of the Merrimac River, Mo. I wish 

 to acknowledge favors extended by Mr. C. C. Laney and Mr. John Dunbar, of 

 Rochester, Prof. C. H. Peck, of Albany, and Mr. J. G. Jack, of the Arnold 

 Arboretum, in assistance to material illustrative of various species of Crata?gus 

 of their respective regions. To Mr. E. P. Clapp, Rev. E. J. Hill, Dr. J. 

 Schneck, ^Ir. H. X. Patterson, Prof. B. O. Longyear, Prof. ^Y. A. Buckhout, 

 Prof. A. T. Erwin, Mr. V. R. Gardner, Mr."^ E. S. Steele, Mr. F. E. 

 Boynton, :\rr. T. G. Harbison, Dr. R. M. Harper, :\Ir. B. T. Gault, :\Ir. F. K. 

 Balthis, ]\lr. A. J. Johnson and 'Mr. J. C. Teas, I wisli also to extend thanks 

 for assistance. Last, but by no means least, I gratefully acknowledge counsel 

 and facilities extended in the use of herbarium material by Mr. Gifford Pinchot, 

 Forester, and Mr. G. B. Sudworth, Dendrologist of [he U. S. Forestry Service ; 

 by Dr. J. X. Rose of the National Herl)arium, and by Dr. X. S. Britton, 

 Director of the Xew York Botanical Garden. 



Data as to specific gravities of woods has been taken from the Report of 

 Tenth Census of the United States, and represent in each case the average of 

 two or more determinations with absolutely dry wood taken from different trees. 



LowviLT.E. X. Y., June 29, 1907. 



