1 "Plants with irritant hairs, sometimes sparse" 2 1 "Plants without irritant hairs" 4 2 "Trees; leaves alternate" Dendrocnide 2 "Herbs; leaves opposite or alternate" 3 3 "Leaves opposite" Urtica 3 "Leaves alternate" "Laportea {Laportea interrupta}" 4 "Climbers, vines or lianes" "Nothocnide {Nothocnide repanda}" 4 "Herbs, sometimes creeping, sometimes epiphytic, or shrubs or trees" 5 5 "Herbs, sometimes creeping; stem often woody at base" 6 5 "Subshrubs, shrubs or trees" 11 6 "Male perianth bilabiate; stamen 1; pistillode absent" "Australina {Australina pusilla}" 6 "Male perianth 3-5-lobed; stamens 3-5; pistillode small, usually present" 7 7 "Female perianth 2-4-partite" 8 7 "Female perianth tubular, the orifice 2-5-dentate" 9 8 "Leaves usually alternate, falcate or asymmetric at base" Elatostema 8 "Leaves opposite, usually symmetric" "Pilea {Pilea microphylla}" 9 "Flowers solitary, axillary, subtended by an involucre of 1 bract and 2 bracteoles" "Soleirolia {Soleirolia soleirolii}" 9 "Flowers in clusters of 3 or more" 10 10 "Stipules present at least in young shoots; flowers unisexual; stigma filiform, unilaterally stigmatic; achenes black, smooth, shiny" Pouzolzia 10 "Stipules absent; flowers unisexual and bisexual; stigma sessile to long-styled, subcapitate to capitate with long stigmatic processes; achenes brown, smooth, shiny" Parietaria 11 "Female perianth of 3 or 4 (rarely 5) tepals; leaves opposite, 1 of each pair greatly reduced or some aborted so as to appear alternate; male inflorescence a loose cyme; female inflorescence capitate-globose, sessile to subsessile" "Procris {Procris pedunculata}" 11 "Female perianth tubular, free or adnate to ovary; leaves opposite with 1 of each pair greatly reduced, alternate, or spiralled" 12 12 "Leaves peltate, radially lobed; inflorescence a digitate cluster of spikes inclosed in a spathe" "Cecropia {Cecropia peltata}" 12 "Leaves not peltate or strongly lobed; inflorescence not as above" 13 13 "Stipules entire; stigma persistent or caducous; female perianth tubular, 2-4-dentate" 14 13 "Stipules bifid; stigma caducous; female perianth minutely dentate" 15 14 "Achene dull, remaining enclosed in fruiting perianth; inflorescence spike-like or paniculate" Boehmeria 14 "Achene shining, easily detachable from fruiting perianth; inflorescence a sessile axillary cluster" Pouzolzia 15 "Plants dioecious; inflorescence spicate with flowers clustered into globular heads, forming a multiple fruit; stigma filiform" "Pipturus {Pipturus argenteus}" 15 "Plants monoecious; inflorescence a short cyme; stigma penicillate" "Debregeasia {Debregeasia australis}"