1886.] 293 [Trelease. 



NORTH AMERICAN SPECIES OF THALICTRUM. 



BY WILLIAM TRELEASE. 



Thalictrum is not a large genus. Bentham and Hooker 1 rec- 

 ognize about fifty species, which Lecoyer 2 increases to sixty-nine, 

 twelve of which are attributed to the United States. Watson 3 

 enumerates fourteen coming within our limits. Though our spe- 

 cies are few, they are by no means easily recognized, so that I 

 gladly availed myself of the invitation of Professor Gray to study 

 the numerous specimens contained in his herbarium. Through 

 his kindness these have been supplemented by those in the herbari- 

 um of Columbia College, including the collections of Torrey and 

 Chapman, for which we are indebted to Mr. Britton, and the ad- 

 mirable specimens of J. Donnell Smith of Baltimore and W. M. 

 Canby of Wilmington, Del. It has also been my privilege to ex- 

 amine the American species in the herbarium of Wellesley College, 

 shown me by Miss Hallo well, in the Lapham herbarium of the 

 University of Wisconsin, loaned by Mr. Seymour, and in the her- 

 barium of this Society, placed at my disposal by Miss Carter ; and 

 a number of friends have kindly allowed me to examine their spec- 

 imens of our eastern forms. 4 At the suggestion of Dr. Gray, I 

 have ventured to bring the results of this study together in the 

 following pages. The nomenclature adopted is, in the main, that 

 of his manuscript revision of the genus for the Synoptical Flora, 

 which he has obligingly placed in my hands, so that I shall not 

 enter into the discussion of this question, merely citing such syn- 

 onyms as are necessary for an understanding of the more perplex- 

 ing species. The principal bibliography of the genus is indicated 

 in Watson's Index, already referred to. 



Excluding T. anemonoides, which is now removed to Anemonella, 

 as proposed by Spach, 5 the genus is characterized as follows : — 

 Perennial plants with alternate, ternately decompound leaves, 

 none of them collected into an involucre. Flowers panicled or 

 rarely racemed, apetalous, perfect, dioecious or occasionally poly- 



1 Genera Plantarum, I, 1872, 4. 



4 Monographic du genre Thalictrum, Gand., 1885. (From Bull. Soc. Roy. de Bot. de 

 Belg., 1885-6.) 



3 Bibliographical Index to North American Botany, 25. 



4 Since the presentation of this paper, I have examined the specimens in the Engel- 

 mann herbarium, but without gaining any additional points. 



5 Gray : Bot. Gazette, 1886, xi, 39. 



