| 1 | Flowers in terete spicate conflorescences which arise singly or in threes, terminally and laterally, these sharply distinct from the strongly flattened vegetative cladodes |
| 1' | Flowers produced at nearly all nodes, or predominantly on more slender lateral cladodes, but not in strongly differentiated spicate conflorescences (the internodes of flowering branches showing a gradual rather than an abrupt transition in shape from the lower non-flowering ones) |
| 2 | Flowers 3 in each cluster; conflorescences commonly lateral, sometimes terminal; conflorescence internodes 1-1.5 mm long |
| 2' | Flowers 40 or more in each cluster; conflorescences rarely lateral, mostly terminal; conflorescence internodes 1.5-7 mm long |
| 3 | Internodes terete, without visible veins; plants very slender, up to 3 cm long; hosts conifers |
| 3' | Internodes compressed or flattened in one plane, with 1-3 veins visible as raised ribs; plants slender to robust, mostly more than 5 cm long; hosts dicotyledons |
| 4 | Largest internodes usually 1-ribbed, 5-12 mm long; plants mostly less than 10 cm long; flowers usually 8 or fewer in each cluster |
| 4' | Largest internodes usually 3-ribbed, 10-27 mm long; plants mostly more than 10 cm long; flowers usually more than 10 in each cluster |
