| 
RE ne a ees 
RYDBERG: NOTES ON ROSACEAE oes 
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 sonamed belong to A. elongata. Bitter, in Biblio- 
theca Botanica, 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 (7. 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- 
cana{ admitted four species of Acaena to Mexico, viz. A. agri- 
moniordes HBK., A. elongaia L., A. lappacea | R. &. &. _ and A; 
| 9 Big), * Prantl, Nat. Pflanzenfam. 3°: 45. 
