38 ROYAL SOCIETY OF CANADA 



all present requirements would be met in a satisfactory manner. When 

 special questions have arisen, however, respecting the union or separation 

 of genera or species, e. cj., the separation of Cupressus and Chamœcyparis, 

 or the identity of Cupressus macrocarpa with C. guadalupensis, as sug- 

 gested by Masters,' the nomenclature has been changed to meet the 

 requirements of the particular case. 



In this connection I desire to record my deep appreciation of the 

 very large measure of assistance which has been freely offered by a 

 large number of correspondents. To my friend, Dr. G. L. Goodale, of 

 Harvard University ; to Prof. C. S. Sargent, of the Arnold Arboretum ; 

 Dr. Trelcase, of the Missouri Botanic Gardens ; Dr. Douglass Campbell 

 and Prof Dudley, of the Leland Stanford. Jr., University ; Prof. Lem- 

 mon, of San Francisco; Dr. Charles Mohr, of Mobile, Alabama; Baron 

 F. von Mueller and Mr. Walter Hill, of Australia ; Prof ,Tohn Macoun, 

 of the Geological Survey, Ottawa ; Mr. B. E. Fernow, chief of the Divi- 

 sion of Forestry of the United States Department of Agiculture ; Dr. A. 

 W. Chapman and Dr. B. L. Eobinson, curator of the Gray Herbarium of 

 Harvard University, I am indebted for valuable assistance in securing 

 authentic material and references. To Mr, Morrice K. Jesup, president, 

 and Mr. Dill, secretary of the American Museum of Natural History, 

 New York, I am under obligations for much courtesy in supplying a 

 large amount of valuable material. To Mr. J. G. Jack, of the Arnold 

 Arboretum, I desire to express my special acknowledgments of the assist- 

 ance freely ottered, and, often with much inconvenience to himself, in 

 procuring material and sup])lying authentic si)ecimens for control tests. 

 To Miss C. M. Derick, lecturer in l)otany, McCiill University, I am also 

 under obligations for much assistance in the prosecution of this work. 



The data for a diti'erentiation of the Taxaceœ and Coniferœ arc to be 

 found in the occurivnce of resin-passages, of isolated resin-cells and of 

 medullary rays containing resin-passages, as also in the presence or 

 absence of tracheids with spiral markings. 



The Coniferœ, as a whole, are distinguished by their more or less, 

 often strongly resinous wood. This is found in some cases to be due to 

 the presence of numerous large channels — the resin-passages — which tra- 

 verse the stem longitudinally for great distances, and such structures are 

 always characteristic of Pseudotsuga, Larix, Picea and Pimis, more 

 rarely appearing in an imperfectly organized form in Sequoia and Abies. 

 On the other hand, the resinous matter is found to have its origin in iso- 

 lated resin-cells, which are variously distributed either through the entire 

 body of the growth-ring or localized along the outer face of the summer 

 wood. In either case their presence may be at once determined by the 

 peculiarly dark and resinous colour of the contents, or by the structure 

 of the terminal walls wherever exposed in transverse section. The walls 



J "Garden aiul Forest," vii., 298. 



