Rhipsalis aurea M. F. Freitas & I. M. A. Braga, sp. nov. Syst Bot. 34(3): 505-509. 2009

• Rupicolous or epiphytic, 60-80 cm long.
• Roots stiff, grayish white, adventitious roots absent.
• Branches suberect to almost horizontal or slightly pendent, erect when young, branching
  subacrotonically or mesotonically.
• Stem segments cylindrical; primary of indeterminate growth, basal 15-45 cm long, 4-6 mm diam, suberect, stiff, woody; subsequent 3-4, 14-20 cm long, 3.7-4.7 mm diam, suberect, stiff but succulent, dark green; secondary smaller, of determinate growth, 2-9 cm long, 1.2-3 mm diam, pendent, succulent, dark green.
• Areoles ca. 0.5 mm diamr green, reddish or brown; scales 1-2, ca. 0.5 x 1 mm, triangular; hairs absent in mature segments and present in young segments.
• Flowers 1.6-1.7 x 1.5-2 cm at anthesis, campanulate, not conspicuously immersed in the areoles; absent to 1 per areole, diurnal, inodorous, mostly subapical or lateral, oblique to slightly perpendicular to the stems; pericarpel 0.2-0.3 x 0.4 mm, green to yellow, turbinate, distinctly truncate; perigonium segments golden yellow, immaculate, membranaceous, 0.2-1.3 x 0.3-0.6 mm, gradually longer and thinner towards the center, suborbicular, triangular to oblong, apex rounded, external spreading to suberect, internal erect. Stamens polystichous spreading or with a discrete separation of the internal facing outwards and external facing inwards, yellow; filaments 4-7 mm long; anthers 0.5-0.6 mm long.
• Ovary 1.7-2 mm long, turbinate; style 8 mm, yellow; stigma 4-6 lobed , 2 mm long, yellow, oblong, patent.
• Fruit indehiscent, glabrous: when immature cupulate, strongly truncate, green; when mature 6-7.7 x 6-8 mm, depressed-globose, translucent green. Figures 1-2

Additional Specimens Examined-BRAZIL. Estado do Rio de Janeiro, municipio de Nova Friburgo, Macao de Cima, pr. Friburgo, 1,600 m alt., 4 Oct 1959, G. F. J. Pabst 5178 (HB, HBR); Sitio Sophronites,5 Oct1987, G. Martinelli 12252 (RB); Parque Estadual dos Tres Picos, Sitio Vale dos Sonhos, 22°19'43.6" S, 42°43' 27.5" W, 1,702 m alt., 23 Nov 2005, A. M. Calvente and L. M. Versieux 156,157 (RB, SPF).

Discussion

Rhipsalis aurea is a microendemic, rare plant. It is known only from five collections from three different localities in the Tres Picos State Park in the city of Nova Friburgo, Rio de Janeiro State, located in the Serra dos Orgaos. It occurs in high altitude forest between 1,200 and 1,700 m elevation. The vegetation of this region is the Brazilian Atlantic Forest where
epiphytic Cactaceae are an important component (Calvente et al. 2005). Rhipsalis is particularly well represented in the epiphytic flora of this vegetation and in the Nova Friburgo
region nine species are found (Freitas 1996; Fontoura et al. 1997; Calvente et al. 2005). In addition to housing a state park, Nova Friburgo area is known for its rural activities and many
agricultural and cattle raising farms are found there. Two of the locations where the new species was found show no adequate conservation conditions. One of them is adjacent to an
access rcad (Braga 7494) and the other one is next to a pasture inside the main site of the park (Calvente 156,157). These populations should be monitored to have their conservation
assured. Following the IUCN (2001) criteria this new species is vulnerable (VU, B1abiii, iv) due to its restricted area of occurrence and reduction of the quality of habitat observed in
the present and projected for the future.

The newly described species belongs to the subgenus Erythrorhipsalis, which is morphologically distinct in having campanulate flowers not conspicuously immersed in the areoles (Barthlott and Taylor 1995). Within this subgenus, R. aurea is most similar to R. pulchra, having mesotonically to subacrotonically branched stem segments, the primary of indeterminate growth (i.e. with variable length), and characteristic oblique campanulate flowers. However, R. aurea is distinct in having the primary stem segments stiff and the secondary stem segments smaller and with determinate growth (Figs. 1-2). These stem characters are also reflected in a quite distinct habit while R. pulchra is long pendent, R. aurea is smaller and suberect. In addition, R. aurea is markedly different in its golden yellow flowers and by the depressed-globose translucent green fruits. Rhipsalis pulchra has pinkish-white flowers and dark purple to white fruits (Table 1). Loefgren (1915) described R. pulchra originally from Serra da Mantiqueira, but it can also be found in the Serra dos Orgaos.
The mesotonic to subacrotonic branching pattern of both R. aurea and R. pulchra are characteristic of species of Lepismium Pfeiffer as defined by Barthlott (1987). However, neither species has the connate petals forming a floral tube and the angular pericarpel considered to be diagnostic features for Lepismium species (Barthlott1987). The flowers of R. aurea are similar to the flowers of Hatiora salicornioides (Haw.) Britton & Rose in shape and color. However, the morphological characters of R. aurea do not match the features of Hatiora Britton & Rose, all species of which have all stem segments with determinate growth and terminal flowers (Barthlott and Taylor 1995).

Epidermis anatomy has proved useful for separating closely allied Rhipsalis species (Calvente et al. 2008). Epidermis and pollen grain features also segregate R. aurea from R. pulchra. The epidermis of R. aurea has smaller stomata located at the same level as the regular epidermal cells, differing from the bigger sunken stomata complex found in R. pulchra (Fig. 3). In addition, pollen grains of R. aurea are solitary and the exine is conspicuously spiculate, unlike the pollen grains on R. pulchra, which are isolated or in tetrads. The exine of the latter species is punctate and does not possess spicules (Fig. 3).

The first collection of R. aurea was made in 1959 (Pabst 5178) and was kept in the herbaria HB and HBR. The specimen in HB was originally identified as R. gibberula F. A. C. Weber, a synonym of R. floccosa subsp. pulvinigera (C. A. Lindb.) Barthlott & N. P. Taylor. and the specimen at HBR was labeled R. rigida Loefgr., a synonym of R. dissimilis (G. A. Lindb.) K. Schum. Both identifications are erroneous since these specimens do not have the morphological features of either R. floccosa or R. dissimilis, two species that belong to sub genus Epallagogonium and have flowers conspicuously immersed in the areoles. Later, three new collections made it possible to describe R. aurea as a new species and enabled the link with the collection of Pabst 5178. The specific epithet aurea was chosen as an allusion to the golden yellow flowers, not found in any other Rhipsalis species. The flowering period of R. aurea is during the spring and early summer from October to November.