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Hydrangeaceae

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Deutzia
1a. Filaments toothed near apex, dimorphic, the outer ones longer; pith hollow; leaf blades and young branchlets pubescent with stellate hairs
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1b. Filaments without apical teeth, monomorphic; pith solid; plants pubescent with simple hairs or glabrous
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  Hydrangea
  2a. Fertile flowers with 5 petals 1–3 mm long and 10 stamens; marginal flowers of inflorescence often enlarged, sterile, with only 3 or 4 petaloid sepals (enlarged flowers sometimes absent) [Fig. 682]; fruit with 10–15 ribs, dehiscing by pores; winter buds axillary to the petioles
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  Philadelphus
  2b. Flowers with 4 petals 15–30 mm long and 20–40 stamens [Fig. 683]; marginal flowers of inflorescence neither enlarged nor sterile [Fig. 683]; fruit without ribs, dehiscing by longitudinal valves; winter buds embedded in the petiole bases

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