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Protonema

As was stated, a germinating moss or hepatic spore results in a single cell or a group of cells (protonema.) A part of the cells of the more elaborate protonema are without leaf-green (chlorophyll) and seek the darkness afforded by the structure of the substratum in which they serve to anchor the protonema, while they assist in procuring food-materials. Another part of the protonema remains above ground, each cell containing leaf-green and in the light doing its work of converting mineral matter, gases, and liquids into plant foods.

Upon this protonema appear plants which are to produce male and female organisms.

These plants, together with the protonema are known as the first or sexual generation in the life-history of mosses and hepatics, in distinction from the spore-cases which, in connection with their pedicels and "foot" constitute the second generation.

The protonema resembles some of the Thallophytes, examples of which are bacteria, algae, and fungi. The Thallophytes are so called because their vegetative body is a "thallus," that is to say, is not divided into stem and leaf, like that of higher plants, but grows in water or over a substratum in the form of single cells, chains of cells, or ribbon-like patterns of varying designs. The Bryophytes or moss-plants agree in many of their stages of development with the Thallophytes. Many of the liverworts (Hepaticae), one division of the Bryophytes, have never developed further in form than the ribbon-stage or thallus, while others show transitional stages from this ribbon-like form to a leafy stem such as all leafy-mosses possess.