Definition of Protophyta in US English:

Protophyta

noun

Botany
historical
  • With singular or plural concord. A class of primitive plants or plantlike organisms regarded as forming the lowest division of the vegetable kingdom (corresponding to the Protozoa in the animal kingdom), specifically one comprising unicellular and other simple green algae. Also, treated as plural (also protophyta): such plants and organisms collectively.

Origin

Mid 19th century; earliest use found in William Kirby (1759–1850), entomologist and naturalist. From scientific Latin protophyta, plural of protophytum from proto- + ancient Greek ϕυτόν plant.

Pronunciation

Protophyta

/ˌprəʊtə(ʊ)ˈfʌɪtə/