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.
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.
The first wall in the embryo is nearly at right angles to the axis of the archegonium and divides the egg cell into nearly equal parts.
If a ripe archegonium is placed in water, it soon opens at the top, and the contents of the canal cells are forced out, leaving a clear channel down to the egg cell.
I, a ripe archegoniumin the act of opening, × 150.
The neck of the archegonium is quite long, but does not project above the surface of the prothallium (Fig.
Up to this point, all the cells of the embryo are much alike, and the embryo, like that of the bryophytes, is completely surrounded by the enlarged base of the archegonium (compare Fig.
The embryo may be readily removed from the archegonium by adding a little potash to the water in which it is lying, allowing it to remain for a few moments and pressing gently upon the cover glass with a needle.
As the embryo enlarges, the walls of the basal part of the archegonium grow rapidly, so that the embryo remains enclosed in the archegonium until it is nearly full-grown (Fig.
The two growing points on the side of the embryo nearest the archegonium neck grow faster than the others, one of these outstripping the other, and soon becoming recognizable as the first leaf of the embryo (Fig.
To study the first division of the embryo, it is usually necessary to render the archegonium transparent, which may be done by using a little caustic potash; or letting it lie for a few hours in dilute glycerine will sometimes suffice.
As in the liverworts the young embryo is completely covered by the growing archegonium wall.
When very young the archegonium is composed of an axial row of three cells, surrounded by a single outer layer of cells, the upper ones forming five or six regular rows, which are somewhat twisted (Fig.
A single archegonium may arise from the apical cell (Lejeunea); more commonly a number of others are formed from the surrounding segments.
In Marchantia and Fimbriaria an additional investment termed in descriptive works the perianth, grows up around each fertilized archegonium (fig.
The fertilized archegonium develops into a capsule (sporogonium) closely invested by a calyptra, which ruptures above as the ripened capsule (containing numerous spores and usually elaters) pushes upward.
The fertilized nucleus or germ-cell of the archegonium in Cryptogams, from which the new plant is directly developed.
The embryonal cell grows by subdivision, so as to form a stalk-like body, which as it rises extends the archegonium upwards until it splits across near the base.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "archegonium" in a variety of sentences. We hope that you will now be able to make sentences using this word.
