Rydberg: Notes on Rosaceae 323 



question then arises, which of the two species should be called 

 Poteridium annuum. As Nuttall himself afterwards in Torrey & 

 Gray's Flora separated the two, and applied Poterium annuum 

 to the eastern plant and P. occidentalis to the western one, it is 

 best to apply the names in that way. 



POTERIUM 



This genus resembles Sanguisorba in habit, but the stamens in 

 the staminate flowers are numerous and declined; the pistils are 

 usually 2, and the stigmas brush-like. Linnaeus originally had 

 two species in this genus, of which the first, P. Sanguisorba, for 

 several reasons must be regarded as the type. To use Poterium 

 for the second species, P. spinosum L., as Focke has done,* is 

 not correct. For that genus the name Sarcopoterium Spach should 

 be used. 



ACAENA 



This genus has been taken in its narrower sense, excluding the 

 genus Ancistrum. 



Acaena agrimonioides HBK. I have seen no specimens 

 agreeing with the original description of this species. All speci- 

 mens seen and so named belong to A. elongata. Bitter, in Biblio- 

 theca Botanica.f cited it as a synonym and on page 324 he stated 

 that it is "to be regarded as synonymous with A. elongata," but 

 nowhere does he give any reason for so doing. In the original 

 diagnosis of A. agrimonioides, the leaflets are described as being 

 8-10 lines (i. e., 16-20 mm.) long, and the lower gradually smaller. 

 In all specimens of A. elongata I have seen from Mexico the leaflets 

 are rarely 15 mm. long and the lower pairs scarcely smaller than 

 the upper. Although A. agrimonioides is unknown to me and 

 my description in the North American Flora was drawn from the 

 original Latin diagnosis, I can but regard it as distinct from A. 

 elongata. 



Acaena elongata L. Hemsley in his Biologia Centrali-Ameri- 

 canaj admitted four species of Acaena to Mexico, viz. A. agri- 

 monioides HBK., A. elongata L., A. lappacea R. &. P. and A. 



* Engl. & Prantl, Nat. Pflanzenfam. 3 3 : 45. 

 t74: 28. 

 %i: 378. 



