FOREWORD. 



While at the University of Wisconsin, nearly forty years 

 ago, I became interested in the differences by which woody 

 plants may be recognized in winter sometimes more surely 

 than when in flower and learned from Willkomm's excellent 

 but inconveniently shaped book how readily these differences 

 may be grouped for differential purposes. A large collection 

 of winter twigs was accumulated subsequently at the Missouri 

 Botanical Garden, and I owe a lasting debt of gratitude to 

 many friends among them the even then venerable Dr. Chap- 

 man of Florida who collected such material for me. 



Willkomm's book, like other contemporary publications 

 of its kind, was confined to the commonest deciduous trees 

 and shrubs of northern Europe. My intention at that time 

 was to prepare a winter manual of the trees native to the 

 Eastern United States, and illustrations of many of these were 

 prepared by Miss Grace E. Johnson (now Mrs. George Clifford 

 Vieh). For a variety of reasons, this undertaking was laid 

 aside, and her skilful and expressive drawings remain un- 

 published except for those picturing Acer, Carya, Juglans and 

 Leitneria. It is a pleasure to record that though long out 

 of practice, Mrs. Vieh has prepared for the engraver some of 

 the simplified drawings now published. 



Urbana, Illinois, 

 August 1918. 



