prothallium

The sexual generation is a small green thalloid structure called a prothallium, which bears antheridia and archegonia, each archegonium having a neck-canal and oosphere, which is fertilized just as in the moss.

Scientific American Supplement, No. 531, March 6, 1886 Various

The sexual plant, which is here called the "prothallium," is of very simple structure, resembling the lower liverworts usually, and never reaches more than about a centimetre in diameter, and is often much smaller than this.

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell

Comparing this now with the development of the sporogonium in the bryophytes, it is evident that the young fern is the equivalent of the sporogonium or spore fruit of the former, being, like it, the direct product of the fertilized egg cell; and the prothallium represents the moss or liverwort, upon which are borne the sexual organs.

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell

The other (_f_) has no definite form, and serves merely as an organ of absorption, by means of which nourishment is supplied to the embryo from the prothallium; it is known as the foot.

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell

It is filled with a colorless tissue, the prothallium, and if mature, with care it is possible to see, even with a hand lens, two or more denser oval bodies (_ar. _), the egg cells of the archegonia, which here are very large.

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell

After a time growth ceases, and is not resumed until the development of the female prothallium and archegonia is nearly complete, which does not occur until more than a year from the time the pollen spore first reaches the ovule.

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell

As soon as the fern is firmly established, the prothallium withers away.

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell

In both cases the prothallium is small, and often scarcely protrudes beyond the spore, and may be reduced to a single archegonium or antheridium (Fig.  71, _B_, _C_) with only one or two cells representing the vegetative cells of the prothallium (_v_).

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell

It has long been known that after fertilization of the egg has taken place, the formation of endosperm begins from the endosperm nucleus, and this had come to be regarded as the recommencement of the development of a prothallium after a pause following the reinvigorating union of the polar nuclei.

Encyclopaedia Britannica, 11th Edition, Volume 2, Part 1, Slice 1 Various

The neck of the archegonium is quite long, but does not project above the surface of the prothallium (Fig.  77, _H_).

Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Douglas Houghton Campbell