question: Which has more species, Sinowilsonia or Azolla?
answer: Azolla
context: Title: Salviniaceae
  Passage: Salviniaceae (or formerly Salviniaceæ) is a family of heterosporous ferns in the order Salviniales.  The Salviniaceae contain the two genera "Azolla" and "Salvinia", with a total of ca 20 known species.  "Azolla" was previously placed in its own family, Azollaceae, but recent research has shown "Azolla" and "Salvinia" to be sister genera with the likely phylogenic relationship shown in the following diagram.
  Title: Sinowilsonia
  Passage: Sinowilsonia is a monotypic genus of plant containing the single species Sinowilsonia henryi.  It is endemic to China.  It is threatened by habitat loss.
  Title: Azolla cristata
  Passage: Azolla cristata , the Carolina mosquitofern, Carolina azolla, or water velvet, is a species of "Azolla" native to the Americas, in eastern North America from southern Ontario southward, and from the east coast west to Wisconsin and Texas, and in the Caribbean, and in Central and South America from southeastern Mexico (Chiapas) south to northern Argentina and Uruguay.
  Title: Azolla
  Passage: Azolla (mosquito fern, duckweed fern, fairy moss, water fern) is a genus of seven species of aquatic ferns in the family Salviniaceae.  They are extremely reduced in form and specialized, looking nothing like other typical ferns but more resembling duckweed or some mosses.
citations: Azolla Sinowilsonia