Hsiao Pei-Ken, Wang Wen-Tsai
1964, 9 (4): 315–334
The genus Isopyrum was established by Linné in 1742. In Species Plantarum ed.
I: 557 (1753) he discriminated three species under this genus, i.e., Isopyrum fumarioides,
I. thalictroides and I. aquilegioides. The first was, however, separated by Reichenbach
as a monotypic genus-Leptopyrum in 1828, and according to Drummond & Hutchinson
the third species I. aquilegioides proved to be Aquilegia viscosa Gouan. Thus, the only
remaining species, I. thalictroides Linn. naturally constitutes the type of the genus Isopyrum.
Since then, many new species had been discovered, some of which were later separated as distinct genera by different authors. In 1920 Drummond & Hutchinson
published an elaborated revision of the genus Isopyrum, where, when recognizing Leptopyrum, Souliea, Semiaquilegia as distinct genera, and also restoring the validity of
Enemion, they furthermore proposed two new genera: Asteropyrum and Paraquilegia.
In addition to the seven genera above mentioned, Ulbrich further established a new
genus Paropyrum in 1925, and another new genus Urophysa in 1929, basing on Isopyrum anemonoides Kar. et Kir. (=Paraquiligia uniflora [Aitch.] Drumm. et Hutch.)
and I. henryi Oliv. (=Semiaquilegia henryi [Oliv.] Drumm. et Hutch.) respectively.
Our present study has shown that Asteropyrum, Paraquilegia, Leptopyrum, Semiaquilegia, Souliea, Enemion, Usophysa are all remarkably distinct genera. As for genus
Urophysa, it reveals a very close affinity to Aquilegia in having stamanoides inside the
fertile stamens, the long-styled carpels and the similar nectariferous petals; but the
more simply divided leaves and the less conspicuous nectariferous organs seem to show
that the genus is more primitive than Aquilegia.
After a careful examination of the species of genus Isopyrum Linn. s.1. and of its
near allies, we find that I. thalictroides Linn., I. anemonoides Kar. et Kit. (=Paropyrum
anemonoides [Kar. et Kir.] Ulbr.) and I. manshuricum Kom. (=Semiaquilegia manshurica
Kom. and I. manshuricum Kom.) are homogenous both in habit and floral structure,
thus forming a very natural group. The genus Isopyrum Linn. itself, while remaining
sixteen species, however, form another natural group, which is easily distinguished from
Isopyrum by a series of important characteristics, for which we propose a new genus,
Dichocarpum. On account of the foregoing reasons, it is suggested that Paropyrum
Ulbr. will not uphold as a separate genus, and we also feel necessary to amend the cir-cumscription of Isopyrum as construed by Drummond and Hutchinson.