• Plant - usually creeping over rocks, freely rooting, appressed, somewhat branching.
• Branches - foliaceous, usually flat, sometimes 3, 4, or even 5-angled, linear, lanceolate, 2 cm. broad, narrowed at base, more or less purplish, especially on edges; margins somewhat repand; areoles sunken in margins.
• Flowers - white, 2 to 5 or even more from an areole, 12 to 13 mm. long.
• Fruit - globular, juicy, purplish to red, translucent, 6 to 12 mm. in diameter.
• Seeds - light brown to black, 1.8 mm. long.
• Type locality - Coast of Brazil.
  
  DISTRIBUTION - Brazil (Pernambuco, Bahia, Minas Gerais, Espirito Santo, Rio de Janeiro, Sao Paulo, Mato Grosso do Sul, Parana, Santa Catarina, Rio Grande do Sul.), Paraguay, Argentina (Corrientes, Misiones, Chaco): epilithic and epiphytic, on coastal rocks and in seasonal forest (brejo forest in NE Brazil), sea level to 1200 m altitude.

Info from Bradleya 13

The date of 1825 accepted for the publication of Vellozo's Florae fluminensis by Britton and Rose (1923) was incorrect and has necessitated a proposal to conserve the name Cactus cruciformis Vellozo over various priorable synonyms (Taylor 1994).

This species is enormously variable in habit and flower colour (cream, yellow, pink, or rarely magenta), such variation being partly linked to ecological factors. The extreme forms are probably of neotenic origin, resulting in slenderly cereoid plants with up to 6 ribbed stems and tiny flowers, which contrast strongly with larger-flowered forms with flattened axes up to 7 cm or more broad. Further study may enable some of these to be given formal recognition, but at present this variation appears to be more or less continuous. 

Desc from Hunt 2006.

Branch segments very variable, 3-6 angled, ribbed or winged, or flat, up to 50 x 1-7cm, usually suffused purple, margins more or less deeply crenate; areoles in the crenations, tufted with white hairs, subtended by a scale-like leaf rudiment; flowering areoles immersed; flowers lateral, 1-5 per areole, 10-13mm, almost white; pericarp somewhat emmersed; outer tepals tinged red or brown; fruit sub-globose, ca 6mm diam, purple red.

 

The plant below is sold by Tropiflora as R. curciforme (Hans Wehler). Tropiflora appends the name of the source of their Rhipsalis. This form seems to be different from the typical cruciforme in the trade.