What does "protophyte" mean?

Protophyte: Any unicellular plant, or plant forming only a plasmodium, having reproduction only by fission, gemmation, or cell division. Note: The protophytes (Protophyta) are by some botanists considered an independent branch or class of the vegetable kingdom, and made to include the lowest forms of both fungi and algæ, as slime molds, Bacteria, the nostocs, etc. Cf. Carpophyte, and Oöphyte.