This revision deals with the system, evolution, distribution, cytotaxonomy and
taxonomic treatment of the genus Aristolochia Linn. from E. & S. Asia, which covers Japan,
USSR (Far East), China, Viet Nam, Laos, Cambodia, Thailand, Burma, India, Bhutan, Ne-
pal, Sikkim, Bangladesh and Pakistan. Total 2 subgenera, 7 sections, 4 series, 68 species and
1 variety (cultivated species not included) are recognized in this treatment, of which 3 sec-
tions and 2 species are described as new. In addition, 13 new synonyms and some new re-
cords to this region are also included.
Ystem Having estimated all the works dealing with the subdivision of the genus by
the previous authors, the system of O. C. Schmidt (1935) is chosen as the basis, with a change
of the sequence of the subdivisions. The subgenus Pararistolochia (Hutch. & Dalz.) O. C.
Schmidt, which has indefinite stamens and gynandrous lobes, seems to be better considered as
the most primitive one in the genus, while the subgenus Siphisia (Raf.) Duch., which has de-
finite stamens and gynandrous lobes, anthers arranged in 3 pairs and more modifications of
the perianth, seems to be the most advanced one. The perianth of the subgenus Siphisia has dif-
ferentiated into several types, and it is more rational using this character to classify sections
than lobes of the gynostemium. In this way, three new sections has been established. A sug-
gested system of the genus is summarized as follows:
Subgen. 1. Pararistolochia (Hutch. & Dalz.) O. C. Schmidt
Subgen. 2. Aristolochia: Sect. 1. Aristolochia (2 series), Sect. 2. Gymnolobus Duch.
Subgen. 3. Siphisia (Raf.) Duch.: Sect. 3. Pentodon Klotz, Sect. 4. Odontosiphisia J. S.
Ma, Sect. 5. Leptosiphisia J. S. Ma, Sect. 6. Nepenthesia Klotz., Sect. 7. Obliquosiphisia J. S.
Ma, Sect. 8. Siphisia (2 series).
Evolution According to the character analysis of the genera of Aristolochiaceae, the ev-
olutionary trends of the family are proposed as follows: 1, the perianth from double to single,
from cup-like to tubular, 2, stamens from indefinite to definite, from separate from pistil to
united into a gynostemium with pistil, which is a major evolutionary line in the family, 3,
ovary from half-superior to inferior, and 4, fruit from a follicle to a capsule. It is evident
that the genus Aristolochia, with a tubular perianth, stamens 6, a gynostemium, an inferior
ovary and a capsule, is in highly advanced position in the family. The subgenus Pararistolo-
chia, which has more stamens and more lobes of gynostemium, is very similar to the genus
Thottea Rottb. and thus better considered as the most primitive subgenus in the genus. The sub-
genus Siphisia, which has definite stamens (6) in 3 pairs and 6 lobes of gynostemium as well
as the polyploid feature (2n=4x=28), is the most advanced subgenus. As a result of the char-
acter analysis, the evolutionary trends of the subgenera in the genus, which are in accordance
with those of the family, are proposed as follows: 1. stamens from indefinite to definite, and
2. gynostemium lobes from more to less.
Distribution The more primitive subgenus Pararistolochia is only distributed in West
Africa (except 1 species in Malesia), the subgenus Aristolochia in the tropical and subtropical
regions, rarely in the temperate one, and the most advanced subgenus Siphisia occurs mainly
in E. Asia, occasionally in N. America. The result of this work shows that the Hengduan
Mountains is the second center of distribution after South America. The second center of dis-
tribution is of following features: 1. complex composition of taxa, among 3 subgenera and 8
sections, 2 subgenera and 7 sections have been recorded here, 2. rich in species, more than
half of the total E. & S. Asian species, i.e. about 42 species have been found in this region, and
3. numerous endemics, more than 85 percent of the total number of species in the region, i.e.
about 35 species, are endemic.
Cytotaxonomy and taxonomic treatment The known chromosome numbers in 43
species, with 34 reported by Gregory (1956) and Fedorov (1969), together with 9 species newly
reported in this work, show that Subgen. Aristolochia with 2n=2x=14, rarely 12, is apparently
more primitive than Subgen. Siphisia with 2n=2x=28.
