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A New Genus of Ranunculaceae—Dichocarpum W. T. Wang et Hsiao
Hsiao Pei-Ken, Wang Wen-Tsai
Acta Phytotaxonomica Sinica. 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 Iso- pyrum. Since then, many new species had been discovered, some of which were later se- parated as distinct genera by different authors. In 1920 Drummond & Hutchinson published an elaborated revision of the genus Isopyrum, where, when recognizing Lepto- pyrum, 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 Iso- pyrum 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, Semia- quilegia, 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 a
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