VOL. I. INTRODUCTION. ix 



Nomenclature. 



The names of genera and species used in this work are in general accordance with the 

 Code of Nomenclature recommended by the Nomenclature Commission of the Botanical 

 Club of the American Association for the Advancement of Science, published in Bulletin of 

 the Torrey Botanical Club 34: 167-178, 1907, to which reference is made. The synonyms 

 given under each species in this work include the recent current names, and thus avoid any 

 difficulty in identification. 



The necessity for rules of nomenclature arose from the great confusion that has existed 

 through the many different botanical names for the same species or genera. Some species 

 have had from 10 to 50 different names, and, worse still, different plants have often had the 

 same name. For about 200,000 known species of plants there are not fewer than 700,000 

 recorded names. Such a chaotic condition of nomenclature is not only extremely unscien- 

 tific, burdensome and confusing in itself, but the difficulty and uncertainty of identification 

 which it causes in the comparative study of plants made it a serious and constant obstruction 

 in the path of botanical inquiry. 



The need of reform, and of finding some simple and fixed system of stable nomen- 

 clature, has long been recognized. This was clearly stated in 1813 by A. P. DeCandolle in 

 his "Theorie filementaire de la Botanique " (pp. 228-250), where he declares priority to be 

 the fundamental law of nomenclature. Most systematists have acknowledged the validity of 

 this rule. Dr. Asa Gray, in his "Structural Botany," says (p. 348): "For each plant or 

 group there can be only one valid name, and that always the most ancient, if it is tenable; 

 consequently no new name should be given to an old^plant or group, except for necessity." 



This principle was applied to Zoology in the " Stricklandian Code," adopted in 1842 as 

 Rules of the British Association, and revised in 1860 and 1865 by a committee embracing the 

 most eminent English authorities, such as Darwin, Henslow, Wallace, Clayton, Balfour, 

 Huxley, Bentham and Hooker. In American Zoology the same difficulties were met and 

 satisfactorily overcome by a rigid system of rules analogous to those here followed and now 

 generally accepted by zoologists and palaeontologists. 



At an International Botanical Congress held at Paris in 1867, A. DeCandolle presented a 

 system of rules which, with modifications, were adopted, and are the foundation of the 

 present rules of the botanists of the American Association. These rules were in part 

 adopted also by the International Botanical Congress held at Genoa in 1892, and by the 

 Austro-German botanists at their meeting in September, 1904. 



The Botanical Club of the American Association for the Advancement of Science 

 adopted rules for Nomenclature at meetings held in 1892 and 1893, which were followed in 

 our first edition. An International Botanical Congress assembled at Vienna in 1905, and 

 materially modified the Paris rules of 1867, and another Congress was held at Brussels in 

 1910. In the present edition the Code of Nomenclature recommended by the American 

 Commission in 1907, is closely followed, as above stated. 



Types of Genera and Species. 



The critical study of plants, resulting in the present knowledge by botanists of many 

 more genera and species than formerly, has made necessary more exact definition and 

 determination of both genera and species by basing them on types, a method previously 

 reached in zoology. The following principles are contained in the Code of Nomenclature 

 above referred to : 



i. The nomenclatorial type of a species or subspecies is the specimen to which the describer 

 originally applied the name in publication. 



(a) When more than one specimen was originally cited, the type or group of specimens 

 in which the type is included may be indicated by the derivation of the name from 

 that of the collector, locality or host. 



(&) Among specimens equally eligible, the type is that first figured with the original 

 description, or in default of a figure the first mentioned. 



(c) In default of an original specimen, that represented by the identifiable figure or (in 

 default of a figure) description first cited or subsequently published, serves as 

 the type. 



