ROBINSON. — ALSINEiE. 273 



i 



XIV. 



CONTRIBUTIONS FROM THE GRAY HERBARIUM OF HARVARD 

 UNIVERSITY, NEW SERIES, NO. VI. 



By B. L. Robinsox. 



Presented January 10, 1894. 



I. — THE NORTH AMERICAN ALSINEIE. 



The following provisional treatment of the North American 

 Alsinece is based principally upon the material in the Gray Herbarium. 

 An effort, however, has been made to see as large a representation of 

 the group as possible, and with this end in view a number of other 

 large and valuable collections have been visited ; namely, the herbaria 

 of the Department of Agriculture, Columbia College, the Missouri 

 Botanical Garden, the Philadelphia Academy of Natural Sciences, the 

 Boston Natural History Society, and the private collections of 

 Mr. William M. Canby of Wilmington, Del., Mr. John Donnell 

 Smith of Baltimore, and Mr. Walter Deane and Mr. Edward L. Rand of 

 Cambridge, Mass. Those in charge of all these collections have most 

 kindly allowed their Caryophyllacece to be examined, and all such 

 specimens as showed any noteworthy peculiarities to be brought to 

 Cambridge for critical study. From the herbaria of the Canadian 

 Geological Survey, Iowa Agricultural College, and Natural History 

 Society of Wilmington, Del., the entire representation of Alsinece 

 has also been most obligingly forwarded to the Gray Herbarium for 

 examination. 



While the study of such copious materials has obvious advan- 

 tages, it by no means lessens, but rather increases, the difficulties of 

 classification. In a long series of specimens individual variation 

 becomes apparent in a way which can scarcely be realized if study is 

 confined to fewer plants. Specific limitations often become very 

 obscure, and sharp definition almost or quite impossible. Several 

 instances of such practically confluent species occur in the present 

 group, and in adjusting specific lines there is consequently great room 

 for difference of opinion. Free criticism and friendly aid will be very 

 vol. xxix. (n. s. xxi.) 18 



