Mr. Bentham oti the Eriogonese, a Tribe of the Order Polygonacese. 403 



Eriogomim viminemn, it M-ill be admitted that the two series cannot be other- 

 wise considered than as forming one natural order. The medical properties 

 of several species of Erlogonum (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 Polygotiacece, 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. 



Gyncecium 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 Eriogonece (Tab. XVII. fig. I.) we have 

 the regular normal state above described. In Rumex (Tab. 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 (Tab. 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. 3 G 



