New names in Rhipsalidinae (Cactaceae)
Key to the 4 genera in Rhipsalideae Tribe
Botanisches Institut der universitat Bonn
MeckenheimerAllee 170, D-5300 Bonn, West Germany
to be used in forthcoming treatments (this was posted in 1999) of Rhipsalis
and allied genera (Cactaceae subtribe Rhipsalidinae Britton
& Rose) is briefly explained, and 26 new names proposed.
After extensive discussion,
a Working Party of the International Organization for Succulent Plant
Study (IOS), of which the author was a member, recently recommended
the acceptance of five genera in the Rhipsalis group (Hunt, D.
R. & Taylor, N. P., eds., in Bradleya 4: 65-78(1986), Group
II), with the reservation that two of the genera, Lepismium and
Pfeiffera, might be combined but for the confusion likely to
arise from the amplification of Lepismium (the older name) in
a sense very different from that proposed by Backeberg (Die Cactaceae
2: 682-697.1959). Enquiries were subsequently made concerning the possibility
of conserving the name Pfeiffera, but it is understood that a
proposal to this end would be unlikely to succeed and that the priority
rule would have to take its course. Even so, the author feels that the
taxonomic grounds for combining the two genera must override nomenclatural
considerations and the Pfeiffera-Lepismium merger should go ahead.
changes necessitated by the IOS Working Party's report and by the author's
decision to amplify Lepismium are made below so that the new
names will be available for use in a treatment of the Cactaceae
for Kubitzki et al., The Families and Genera of Vascular Plants,
and in detailed treatments of Rhipsalis and allied genera which
are in preparation.
The proposed framework
of genera and subgenera in the Rhipsalidinae is based on morphological
(vegetative and floral) and micromorphological investigations (predominantly
SEM [Scanning Electron Microsopy] studies of seedcoats and epidermises)
carried out by the author and others between 1971 and 1986. In addition,
papers on the systematics of the family as a whole, notably the survey
of pollen-morphology by B. E. Leuenberger (Diss. Bot. vol.31, Vaduz
1976), the various publications on individual species and genera by
M. Kimnach (in Cact. Succ. J. (US), vols. 28-57.1956-1985) and
the recently published survey of the Rhipsalidinae by S. A. Volgin
(in Feddes Repert. 97: 553-564.1986) have been fully considered.
The four genera
recognized here form a natural group and are probably not closely related
to the other epiphytic genera of Cactaceae; there is evidence that the
great resemblance with some Hylocereinae (notably the genus Pseudorhipsalis)
is a result of convergent adaptation to the same epiphytic habitat.
No hybrids between
the genera ( or even the subgenera) accepted here are known. On the
basis of seed-morphology, and various other characters, the Rhipsalidinae
seem to have had a common origin with the South American tribe Notocacteae
F. Buxb. (resembling most closely the genus Corryocactus).
and possible phylogenetic relationships of the component genera and
subgenera of the Rhipsalidinae are summarized in the following
key. The scheme will be justified in more detail in future papers devoted
to the individual genera.
system mesotonic: pericarpel tuberculate and spiniferous or angled.
rarely almost terete: spines often hard; scale-leaves often clearly
visible (centre of diversity Bolivia and Argentina, a few spp extending
NE into Brazil)
system acrotonic. very rarely mesotonic; pericarpel usually terete
and naked (bristly in some spp. of Rhipsalis subg. Erythrorhipsalis;
angled in 2 spp. of Hatiora and 3 spp. of Schlumbergera);
spines absent or, if present, soft (centre of diversity E BraziI,
a few spp. extending throughout trop. America, Africa Madagascar
2a. At least some of the stem segments longer than 5cm: flowers
more or less whitish, never intensely coloured: tips of stem-segments
without a clearly defined composite areole (except Rhipsalis
|2b. All stem-segments
less than 5cm, flowers intense yellow, pink or red (except white
forms of Schlumbergera spp.); tips of stem-segments with
a composite areole (except neotonic taxa and individuals)
3a. Flowers actinomorphic; tube shorter than 5mm
mostly zygomorphic; tube longer than 8mm