Mr. Bentuam on the Eriogonee, a Tribe of the Order Polygonacee. 403 
Eriogonum vimineum, it will be admitted that the two series cannot be other- 
wise considered than as forming one natural order. The medical properties 
of several species of Eriogonum (called in America Wild Rhubarb) are also 
known to have much similarity to those of Rheum. 
Meisner, in his above-quoted monograph of Polygonum, in speaking of the 
number of parts in the organs of fructification of that genus, follows De Can- 
dolle in considering the normal number of stamina to be double that of the 
lobes of the perianthium, and the several variations observable in the different 
species to be due to the abortion of stamina only. There appear, however, to 
be several objections to this theory. It is not probable that in an order varying 
as much in the number of lobes of the perianthium as in that of the stamina, 
the number of lobes nevertheless should be constantly normal, whilst there is 
as constant a reduction of number in the stamina, and in those genera where 
the flowers are perfectly regular in their arrangement (as in Rheum, Eriogo- 
num, &c.), the symmetry would be disturbed by the insertion of the stamina 
requisite to make up the number. I should rather suggest that, in the great 
mass of Polygonacec, the normal arrangement of all the parts of the flower is 
ternary, as follows : 
Perianthium double, three external and three internal segments. 
Stamina in three rows, of three each, those of the external row alternating 
with the internal segments of the perianthium, those of the central row 
opposed to them, and the inner ones again alternating with them. In 
most cases, however, these three rows are so closely connected as to give 
the appearance of nine stamina in a single row. 
Gynecium single. Ovarium triangular, with three styles and stigmata. 
The different reductions from the above number will be better understood 
from the accompanying sections, copied chiefly from the plates in Meisner's 
monograph. Thus in Rheum and the Eriogonee (Tas. XVII. fig. 1.) we have 
the regular normal state above described. In Rumex (Tas. XVII. fig. 2.) the 
ternary arrangement still prevails, but the central row of stamina being want- 
ing, the total number is reduced to six, whilst the other parts of the flower 
remain complete. In Atraphaxis (Tas. XVII. fig. 3.) the flower is still regular, 
and the number of stamina, as in Rumex, is only six, but the reduction is 
VOL. XVII. 3G : 
