1	"Flowers mostly more than 4 cm wide with a pronounced tube; stem not divided into short segments "	2
1	"Flowers mostly less than 4 cm, rarely to 5 cm wide, with tube short or absent or stem divided into segments less than 8 cm long "	3
2	"Flowers pink or red, opening during the day "	Nopalxochia
2	"Flowers white, opening at night "	Epiphyllum
3	"Flowers less than 2 cm long, creamy white, borne on the edges of the stem segments "	4
3	"Flowers mostly brightly coloured (at least the style), borne at or near stem segment tips "	8
4	"Stem flat or 2-winged, at least in part "	5
4	"Stem narrowly cylindrical or angled "	7
5	"Adult stems of 2 kinds: main stem cylindrical, at least at the base, the branches flat and scalloped "	Disocactus
5	"Adult stems more or less the same or, if different, then the flat stem margins with irregular teeth "	6
6	"Stem segments mostly single from the sides of old segments, never in clusters at segment tips "	Lepismium
6	"Stem segments primarily at the tips of old segments and often in clusters, or main stems with lateral segments mostly less than 15 mm long "	Rhipsalis
7	"Stem segments mostly single from the sides of old segments, never in clusters at segment tips "	Lepismium
7	"Stem segments primarily at the tips of old segments and often in clusters, or main stems with lateral segments mostly less than 15 mm long "	Rhipsalis
8	"Flower tube more than 6 mm long; lowermost stamens forming a ring around the style "	Schlumbergera
8	"Flower tube less than 6 mm long; lowermost stamens not forming a ring around the base "	Hatiora