Which cacti has more species, Cereus or Limnanthes?
Cereus (plant): Cereus is a genus of cacti (family Cactaceae) including around 33 species of large columnar cacti from South America. Limnanthes:  The seven species are all native to coastal and adjoining regions (inland valleys, foothills and mountains) of western North America, where they typically grow in marshy habitats, such as the margins of vernal pools.
Cereus