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Fern — Part 1

A germinating spore

produces a plate of cells

(prothallium).

Prothallium bears antheridia

and archegonia. Therefore, prothallium

is gametophyte.

All ferns develop from spores, the spores germinate to form-generally a flat plate of cells (prothallium) large enough to be seen well with the naked eye. The prothallia are heart-shaped and green. They are common around the bases of ferns in the woods and may be found in green-houses where ferns are propagated. The prothallium is the sexual or first generation in the life-history of a fern, for on it are produced the antheridia and archegonia necessary for the production of the embryo which shall grow into a fern plant.

It is not an easy matter to keep clearly in mind the relation of the fern parts and the leafy-moss parts. It will help to do this, if one remember that the criterion by which the decision is to be made is one of origin of parts rather than of function and appearance. A glance at the parallel columns will show that if one employ the origin and position of antheridia and archegonia as a criterion, then the vegetative part of hepatic plants and moss plants is an homologous stage with a fern prothallium.

Again, if one employ as a criterion that which originates from a fertilised archegonium, then the spore-case, foot, and pedicel (sporophyte) of an hepatic and moss are homologous with the spore-cases, fronds, stems, and roots of a "fern-plant" (sporophyte). The sporophyte is known as the asexual generation.