183:?. ] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 455 



NOTES ON HYDROCOTYLE AMERICANA L. 



BY THEODOR HOLM. 



(With Plates xlvi. xi.vii.) 



INTRODUCTION. 



It is the intention to present, under the title " Notes," a series of con- 

 tributions to the life-history of some North American plants ; their man- 

 ner of growth, illustrated by morphological representations of the dif- 

 ferences in the development of their rhizomes, stems, etc.; their germina- 

 tion, and, finally, remarks upon their anatomical structure. But it is to 

 be remarked that it would be difficult to give notes of this kind in any- 

 thing like a systematic order, since the observations are usually made 

 incidentally and at different seasons of the year. I hope, however, to 

 be able to give these notes in such a manner as to give a more or less 

 complete idea of some of our more interesting plants, whose develop- 

 ment and structure has either not been described or is only briefly al- 

 luded to in the systematic works. 



There are many circumstances in the life-history of our plants which 

 are imperfectly known, and, although they may seem to be of little 

 interest, they nevertheless have a certain value for the complete 

 understanding of the organization of the plants, and therefore I do 

 not hesitate to publish these observations under the title ' : Xotes." 

 Furthermore, the differences in the development of the organs may 

 often show several good characters, which ought to be given in the 

 diagnosis of the plants, especially when they admit the distinguishing 

 of otherwise nearly allied species. 



Purely systematic studies have furnished mauy excellent contribu- 

 tions to the knowledge of our flora ; the distribution of plants, their 

 different stations, their liability to variation, etc. ; but it seems more 

 than probable that had botanists given more attention to observations 

 of this kind, and especially to the germination of the plants, a subject 

 that has been much neglected, we should have a better knowledge of 

 the complete life history of our plants, and the systematic studies would 

 at the same time be rendered valuable assistance. 



HYDROCOTYLE AMERICANA L. 



During a collecting trip this fall in the woods along the Eastern 

 Branch of the Potomac, Prof. Lester F. Ward, who has kindly shown 

 me the most interesting localities in the vicinity of Washington, railed 

 my attention to Hydrocotyle Americana, which we found growing in 



