8 ANATOMY OF THE GYMNOSPERMS 



could be discussed with direct reference to the assumed relation- 

 ships based upon external characters. The nucleus of such a 

 type series was found in the Sargent collection of woods derived 

 from his work in connection with the Tenth Census. To this 

 other specimens were added through the courtesy of Professor 

 Sargent and Mr. J. G. Jack of the Arnold Arboretum ; Dr. 

 N. L. Britton of Columbia University, and now Director of the 

 New York Botanical Garden ; Mr. Morris K. Jesup, President 

 of the American Museum of Natural History; and Dr. B. E. 

 Fernovv, then Chief Forester of the United States Department of 

 Agriculture ; also to the late Baron Ferdinand von Mueller of 

 Melbourne, Australia ; Sir W. T. Thiselton-Dyer, late Director 

 of the Royal Gardens, Kew; Mr. E. J. Maxwell of Montreal; and 

 more recently Dr. E. C. Jeffrey of Harvard University ; to all of 

 whom my grateful acknowledgments are due. Yet other speci- 

 mens were obtained by personal collection or from trustworthy 

 collectors whose reputation was sufficient guarantee for their 

 authenticity. In this way it has been possible to include in the 

 present list all of the North American species of the Coniferales 

 as enumerated by Sargent in his Si ha, with the exception of the 

 recently described Juniperus flaccida. Present lack of material 

 has also prevented me from making a critical study of Juniperus 

 barbadensis in order to determine anatomically the identity 

 which Sargent establishes on the basis of external characters ; 

 while the same conditions have also barred a study of Juniperus 

 scopulorum, Sargent, and Cupressus pygmaea, Sargent, with a 

 view to determining their validity as distinct species. 



During the progress of the present studies a large amount of 

 material came to hand from Japan and Australia. Its elabora- 

 tion has afforded much information of the highest value, and it 

 has been considered expedient to incorporate it in the present 

 classification. 



With this material in hand the first step was to secure an 

 accurate diagnosis of each species for each of the three sections 

 usual in such cases, and when it is recalled that, as at present 

 elaborated, this involved a critical study of twenty genera and 



