THE NORTH AMERICAN SPECIES OF NYMPHAEA. 
By Gerrit S. Miter, Jr., and Paut C, STANDLEY. 
INTRODUCTION. 
NOTE BY J. N. ROSE. 
There are some groups of plants whose taxonomy can be fairly 
well understood almost solely from ordinary herbarium material. 
There are others in which it is impossible to understand the true 
relationships from such material alone, and some even in which 
herbarium specimens are almost. useless. Among the last are the 
Cactaceae, many of the tropical Euphorbias, the Crassulaceae, and in 
general all the succulent plants. To be properly understood such 
plants should be seen growing, or should be studied from material 
preserved in alcohol or formalin, since in dry specimens most of the 
important characters are distorted beyond all possibility of recogni- 
tion. Among plants of this kind the Nymphaeaceae must be 
included. Most of our knowledge of the genus Nymphaea, judging 
from the literature of the North American species at least, has been 
derived from the study of dried herbarium material. Asa result, 
different authors have arrived at very different conclusions. Impor- 
tant peculiarities of habit and structure not discernible in such 
specimens have been overlooked, and our knowledge of the genus 
has not kept pace with the advances made in some other groups. 
About ten years ago Mr. Gerrit 5. Miller, jr., became interested in 
the genus Nymphaea from field observations of the plants occurring 
in central New York and in the vicinity of Washington, currently 
regarded as belonging to one species, Study of fresh and formalin- 
preserved material showed that there were important and easily 
recognizable differences between the northern form and that found 
farther south, differences in habit, color, and structure, scarcely to 
be detected in dried specimens. He published a brief paper in 1902? 
stating these differences and recognizing the northern plant as a 
distinct species. About the same time he began to bring together 
fresh material from all parts of North America to facilitate complete 
knowledge of the genus as represented there. This attempt was 
remarkably successful. The plants wherever they occur are well 
known as ‘‘yellow pond lilies,” hence, not only professional botanists, 
1 Proc. Biol. Soc. Washington 15: 11-13. 
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