1. Najas has a highly simplified flower due to adaptation to aquatic life but its phylogenetic origin may be drawn from submerged Hydrocharitaceae.2. The original home of Najas may be regarded as Africa, where many primitive species and many allied genera exist, both of which show a concentric distribution from Africa.3. The flower of Potamogeton may be considered as a reduced inflorescence viz. a central female flower surrounded by 4 staminate flowers, as in the flower of Cyclanthaceae.4. The descent of Potamogeton from Helobiae is not probable and it is rather reasonable to conceive that the genus was derived from Pandanales or Synanthae.5. The phylogeny of the group may therefore be drawn as the following diagram: ...