158 Journal of Agricultural Research voi. xxii. no. 3 



T. polygamum gave mostly negative results or the occasional production 

 of pycnia. T. angustifolium, T. aquilegijolium (5), T. minus, T. minus 

 adiantifolium, and T. polycarpum showed occasionally a weak develop- 

 ment of aecia, but usually only pycnia developed or no infection occurred. 

 T. dioicum, in one case, showed a moderate development of aecia; in 

 all other cases only pycnia developed, or no infection resulted. T. 

 Delavayi and T. sp. (98) (PI. 21, A, B) showed fairly vigorous infection, 

 accompanied in most cases by more or less hypertrophy and usually by 

 well-developed aecia. T. flavum (PI. 21, C) and T. sp. (55) (Pi. 21, 

 D) showed a very vigorous infection accompanied usually by pronounced 

 hypertrophy of the infected leaf and petiole tissue and practically always 

 with the production of well-developed aecia. 



An attempt has been made to check the determination of the species 

 of Thalictrum used in these studies, but this has been difficult because 

 a number of them have produced neither flowers nor fruit, and the leaf 

 characters in this genus are in most cases extremely variable. Specimens 

 of most of the species have been sent to Mr. S. F. Blake, of the Bureau 

 of Plant Industry, Washington, D. C, who has kindly compared them 

 with specimens in the United States National Herbarium and has given 

 his opinion as to the identity of our material. The following list gives 

 the species used above, their sources, and native distribution as accurately 

 as they could be determined. The accession number of this laboratory 

 follows the name of each species. , 



Thalictrum angustifolium L. (6) . Source : Seed from Brooklyn Botanic 

 Garden. Distribution: Central Europe and Asia Minor. 



Thalictrum aquilegifolium L. (5 and 66) . Source : Bobbink and Atkins 

 Nursery Co. Distribution: Europe, Middle and Northern Asia. (No. 

 66 was purchased for T. paniculatum.) 



Thalictrum dasycarpum Fisch. and Lall. (65). Source: Department of 

 Botany, Michigan Agricultural College. Distribution: Northern and 

 central United States and southern Canada. 



Thalictrum Delavayi Franchet (56). Source: Farr Nursery Co. Dis- 

 tribution: Western China. 



Thalictrum dioicum L. (16). Source: LaFayette, Ind. Distribution: 

 Eastern United States. 



Tlialictrum flavum L. (53). Source: Farr Nursery Co. Distribution: 

 Europe, Western Asia, and Asia Minor. 



Thalictrum minus L. (17). Source: An American nursery. Distribu- 

 tion: Europe, Asia, and eastern and southern Africa. 



Thalictrum m,inus adiantifolium (63). Source: Seed from Brooklyn 

 Botanic Garden. Distribution: See T. minus. 



Thalictrum occidentale Gray (115). Source: Corvallis, Oreg. Distribu- 

 tion: Mountains, California to British Columbia. 



Thalictrum, polycarpum S. Wats. (114). Source: Berkeley, Calif. Dis- 

 tribution: California. 



