INTRODUCTION. 11 



To meet as many as possible of these difficulties, common and strik- 

 ing differences in the leaf and fruit forms of a number of trees have 

 been specially pointed out in illustrations or descriptions. 



VALUE OF FULL-SIZED ILLUSTRATIONS. 



Nearly all figures show leaves, etc., of natural size. In the writer's 

 experience, nothing is more helpful, particularly to untrained stu- 

 dents, than illustrations practically the exact size of specimens they 

 will find in the field. In reduced illustrations of the leaves, fruits, 

 and seeds of some trees distinctive characters are lost, so that even 

 specialists find them useless. Reduced figures are used only when the 

 natural sizes of the object are too large for the pages of this book. It 

 is believed, however, that in these cases distinctive characters have 

 not been lost. 



OMISSION OF ARTIFICIAL KEYS FOR IDENTIFICATION. 



Keys leading up to the identification of families, genera, and species 

 are omitted, chiefly to prevent further delay in publication. They 

 appear to be little used, if at all, by lay students, who prefer to 

 identify trees by elimination, i. e., by comparing the specimen with 

 the illustrations until a " picture " is found that " fits." This method 

 is wholly unscientific, but is nevertheless the one which busy, 

 untrained lovers of trees are most likely to follow. 



TECHNICAL NAMES OF TREES. 



The technical nomenclature does not correspond wholly with that 

 of any one author. Tree names adopted here are based upon the 

 generally accepted law of priority, which demands that the earliest 

 tenable name be retained. The period in which this law is here held 

 to be operative is from 1753, when the general application of binom- 

 inal names of plants began. This is in accordance with the usage of 

 most dendrologists. 



Many changes of technical names have been necessary since the 

 publication of the author's u Nomenclature of North American Trees " 

 and " Check List of the Forest Trees of the United States," upon 

 which the nomenclature is based. It is regrettable, but inevitable, 

 that authors should differ in judgment regarding the retention of 

 certain tree names, even if they do accept as a working principle 

 priority of publication for every name used. The intricacies of 

 nomenclatural law are too great to be discussed here, but for the sake 

 of illustrating one of the many points of disagreement among den- 

 drologists, the two names Sequoia wellingtonia and Sequoia washing- 

 toniana, now retained for the bigtree of the California Sierras, are 



