50 LEAFLETS. 



the most perplexing difficulties that its forms present. Has 

 any one hitherto confessed a suspicion that, in our dioecious 

 species the leaves are of one description in the male plant, and 

 of quite another form in the female of the same ? They are 

 often very large plants, insomuch that nothing gets into the 

 herbarium but the inflorescences and one or two of the upper 

 cauline leaves. Familiar with many hundreds of herbarium 

 sheets of this kind of material, I am driven well towards a 

 state of hopelessness by the discovery that in one and the same 

 individual, the basal leaves, such as seldom get into the her- 

 barium, may be found to be perfectly glabrous, while the 

 middle and upper cauline are notably or even strongly pubes- 

 cent. With facts like these confronting me, and many more 

 as perplexing, I am daily and hourly face to face with the 

 discouraging circumstance that, among scores of reputable 

 botanists who have endeavored to describe the species, there 

 are stUl no descriptions of any species in the older books, or 

 even in the newer monographs. This last named fact, how- 

 ever, has confronted, and has been the despair of, a number 

 of good botanists ; and these will be found to have taken up 

 one name for a supposed species at one time, then dropped 

 that and taken up another name for it, because this other later 

 name seemed to carry with it something a little more like an 

 intelligible description of a plant. 



The present paper is devoted mainly to some results of a 

 long and careful study of our white-flowered kinds of Thalic- 

 trum, all of which have usually passed for a single species, and 

 under a name that has varied from generation to generation. 

 With early and middle nineteenth-century writers the name 

 was Thalictrum Cornuti. After the suppression of that 

 appellation the name T. polygamum came into vogue, and 

 most of the specimens in herbaria that are recent have the 

 latter name on the labels ; while in one or more of the twentieth- 

 century books of American botany T. corynellum has displaced 

 T. polygamum. An abstract of the history, and the real or 

 supposed reasons for these consecutive changes of name may 

 well find place here. 



