MANUAL OF THE GKASSES OF THE UNITED STATES 13 



(3) Authors have different concepts of the limits of genera. The genus 

 Triticum was described by Linnaeus. A later botanist thought that many of the 

 species of this genus were different enough to constitute a distinct genus, Agro- 

 pyron, and transferred quackgrass, first described as Triticum repens to Agropyron, 

 as A. repens. 



(4) Authors sometimes misidentify species. Linnaeus described one of the 

 cordgrasses as Spartina cynosuroides. Later, Michaux used the specific name for a 

 different species, (Trachynotia cynosuroides, based on S. cynosuroides L.) This 

 error was corrected and the species described by Michaux was given a new name, 

 S. michauxiana. Only recently the loan of the type of Spartina pectinata Link, 

 poorly described many years earlier, shows that that name is the valid one for 

 the species. 



It will be seen that the differences in names are due in part to 

 differences of opinion as to the generic, specific, or varietal distinctness 

 of forms; in part to lack of knowledge as to what plants have been 

 described previously; and in part to errors of identification. 



All the preceding shows the need of rules of nomenclature. To 

 enable users of this manual to coordinate the names published to 

 date a synonymy 2 has been appended in which all the names pub- 

 lished for grasses in the United States have been arranged under the 

 names here adopted, that is, under the oldest valid name for each 

 species. In determining the valid names of the species the Inter- 

 national Rules of Botanical Nomenclature have been followed. 

 Under these rules certain generic names are conserved though they 

 are not the earliest. The names of genera of grasses on the conserved 

 list are as follows: Tragus, Zoysia, Leersia, Hierochloe, Crypsis, 

 Coleanthus, Corynephorus, Cynodon, Ctenium, Buchloe, Diarrhena, 

 Lamarckia, Glyceria. 



Certain other names of genera are used for different reasons. 

 Digitaria antedates Syntherisma with which it is synonymous. 

 Setaria was proposed as a conserved name at the Cambridge Inter- 

 national Botanical Congress and was referred to a committee along 

 with other names. It was also proposed at the Cambridge Congress 

 (and referred to a committee) that the standard species of Holcus be 

 H. lanatus and of Aira be A. praecox, thus validating Sorghum and 

 Deschampsia. 



The synonymy attempts to record all the effectively published 

 names given to species and varieties described from the United States 

 or known to grow in the United States. In addition many names are 

 given which have been published as synonyms or without sufficient 

 description (nomina nuda). Whether such names have been included 

 depends upon whether they have appeared in such works as the Index 

 Kewensis or have some connection with effectively published names. 

 When a species is transferred from one genus to another, a new name 

 results. The basis of the transfer is given in each case. If the name 

 was published as new the original published locality is given. State- 

 ments enclosed in brackets following the original locality are based 

 upon unpublished evidence. 



Forms (formae) are included in the synonymy so far as they have 

 been indexed in the grass herbarium. The index includes all forms 

 recently published in this country. Misapplied names have not been 

 included among the synonyms but are mentioned in a paragraph at 

 the end of the synonymy of the valid species, and then only names 

 that have appeared in recent manuals are given. 



2 For convenience the names of the genera are arranged alphabetically and under each genus the valid 

 names of the species are given in alphabetic order in boldface type, the synonyms of each species (in italics) 

 being arranged chronologically under the valid name. 



