vi PREFACE 
nation of species was definitely introduced n biological nomenclature, 
unless epee for another species or genus.? 
uring the preparation of this manual, numerous botanists, natural- 
ists, and puts helped continuously by the contribution of specimens 
and of information relating to the vegetation and its distribution, in short, 
doing much to help to make this volume complete. 
Botanists as indieated below kindly prepared the NC for several 
plant-families printed in this volume: POACEAE, by D . S. Hiteheock; 
POLEMONIACEAE, by Dr. E. T. Wherry; su d bin by Dr. 
Pennell; PINGUICULACEAE, by Dr. J. H. Barnhart; LORANTHACEAE, by Dr. 
William Trelease. The text for certain genera was prepared by the follow- 
ing botanists: Iris, Vincet , Odontostephana, Scutellaria, Laciniaria, 
Zinnia, Melanthera, O Cosmos, Emilia, by Mr. E. J. Alexander; 
Philadelphus, by Mr. C. D. Beadle; Crataegus, by Mr. Ivar Tidestrom; 
Tilia, by Mr. B. F. Bush; Physalis, Acanthoxanthium, Xanthium, by the 
late Dr. P. A. Rydberg; Carex, Solidago, by Mr. K. K. Mackenzie; Rud- 
beckia, by Mr. C. L. Boynton and Mr. C. D. Beadle; Helianthus, by Mr. 
E. E. Watson; Coreopsis, by Mr. F. E. Boynton; Bidens, by Dr. Karl 
M. Wiegand. The following genera were revised: Viola, Aster, by Mr. 
E. J. Alexander. Assistance is preparing the text of Philotria and 
of Trillium was furnished by Dr. Harold St. John and Mr. Donald C. 
Peattie, respectively. 
Help in many ways was given by my associates on the botanical staff 
of the Garden. Among those who participated in intensive field-work of 
the past two decades were Mr. Charles A. Mosier, the late Captaim, Paul A. 
Matthaus, and Mr. John B. DeWinkeler. Both the galley and the page 
proof have been read by Dr. Edgar T. Wherry, who also supplied the 
provincial distribution- of the species, checked many of the geographic 
ranges, and furnished data as to habitats and soils. The galley proof was 
read in whole or in part by Mr. Kenneth K. Mackenzie, Dr. N. L. Britton, 
Dr. Roland M. Harper, Mr. Edward J. Alexander, and Miss Bertha Picker- 
ing, while each contributor of generic or family treatments, as indicated in 
the text, read the proofs of these. 
he author is indebted to Dr. John H. Barnhart for advice and 
information on many botanical and bibliographie questions that arose 
throughout the years of preparation of the manuseript and the reading 
, ?' The manuscript of the grasses (POACEAE) was completed several years 
ago and was held i n proof along with other parts of this wo pir It was there- 
fore impracticable 39 bring the nomenelature into aecord with the rules of 
nomenclature which Dr. Hitchcock is now following. This ee also ap- 
plies to the treatment of the’ a (RHINANTHACEAE) by Dr. Pennell, and to 
the on of several other families and genera by others, for which credit is 
giv 
