254 AMERICAN MIDLAND NATURALIST 



desmon. Thalictrum clavaium has already been recognized as 

 sufficiently distinct from T. jociidum typical of the genus as to 

 have been segregated under the name Physocarpum.^ There was, 

 however, an older Physocarpon Necker, (1790). To replace 

 Physocarpmn Bercht. and Presl. I suggest Sumnera, in honor of 

 Dr. George Sumner, an early American botanist, who wrote 

 one of our first works on physiological botany. 



Dr. Greene has already emphasized the great difference 

 between our polygamous and dioicous American Rues and the 

 real typical Rues, of which we have, in the limits of Britton's 

 Illustrated Flora only T. alpinuni a plant with perfect flowers 

 and racemose inflorescence. He has suggested that the allies of 

 T. canadense {i. e., T. Cornviti or T. polyamum Muhl.) constitute 

 "at least subgenerically as Leticocoma"^ a group apart. Either 

 of the above mentioned sections were a more distinctly good 

 genus apart from Thalictrum than Syndesmon, and they would 

 seemingly deserve recognition as genera. Following is a resume of 

 synonymy of some of our American plants: 



Sumnera Nwd., Nom. nov. 



Physocarpum, Bercht., and Presl. 1. c.' (1823), not Physocarpon 

 Necker, Elem., II, p. 164, (1790). 



Sumnera clavata (DC.) Nwd. Physocarpum clavatum Bercht 

 and Presl, 1. c. Thalictrum clavatum DC. Syst. I, p. 171 (1818). 



Leucocoma (Greene) Nwd. Nov. gen., [Subgenus or section 

 Leucocoma Greene, 1. c] 



Plantae aestate florentes dioicae (vel polygamae?), fructibus 

 sessilibus, ovato-oblongis, longitudinaliter striatis, vel nervatis 

 foliis exstipellatis compositis vel decompositis in utroque sexu 

 diversis, floribus paniculatis, petalis nullis, sepalis 4-5, staminibus 

 multis exsertis, aliquando clavatis. Typus. Thalictrum canadense 

 Miller. (7. polygamum Muhl.). 



Leucocoma canadensis (Miller) Nwd. 



Thalictrum canadense Miller, Gard. Diet., Ed. 8, (1768), 

 Thalictrum polygamum Muhl., Cat., 54 (1813), Thalictrum Cornuti 

 T. and G., Fl. N. A. I., p. 38 (1838). 



2. Bercht. and Presl, Rostl. i. Ranunc., p. 14 (1823). 



3. Greene, E. L., Leaflets, II, p. 55, et praec., 89 et seq. (1910). 



Pages 167-206 published January 12, 1914. 

 Pages 207-254 published February i, 19 14. 



