Occasionally in the same plant that bears tetraspores, but more commonly in special ones, there are produced the sexual organs, and subsequently the sporocarps, or fruits, developed from them. The plants that bear them are usually stouter that the non-sexual ones, and the masses of ripe carpospores are large enough to be readily seen with the naked eye. If a plant bearing ripe spores is selected, the young stages of the female organ (procarp) may generally be found by examining the younger parts of the plant. The procarp arises from a single cell of the filament. This cell undergoes division by a series of longitudinal walls into a central cell and about four peripheral ones (Fig. 29, _D_ i). One of the latter divides next into an upper and a lower cell, the former growing out into a long, colorless appendage known as a trichogyne (Fig. 29, _D_, _tr._). The antheridia (Fig. 29, _E_) are hemispherical masses of closely set colorless cells, each of which develops a single spermatozoid which, like the tetraspores, is destitute of cilia, and is dependent upon the movement of the water to convey it to the neighborhood of the procarp. Occasionally one of these spermatozoids may be found attached to the trichogyne, and in this way fertilization is effected. Curiously enough, neither the cell which is immediately fertilized, nor the one beneath it, undergo any further change; but two of the other peripheral cells on opposite sides of the filament grow rapidly and develop into large, irregular masses of spores (Fig. 29, _D_ III, IV). While the plant here described may be taken as a type of the group, it must be borne in mind that many of them differ widely, not only in the structure of the plant body, but in the complexity of the sexual organs and spores as well. The tetraspores are often imbedded in the tissues of the plant, or may be in special receptacles, nor are they always arranged in the same way as here described, and the same is true of the carpospores. These latter are in some of the higher forms, _e.g._ _Polysiphonia_ (Fig. 29, _F_), contained in urn-shaped receptacles, or they may be buried within the tissues of the plant. [Illustration: FIG. 30.--Marine red seaweeds. _A_, _Dasya_. _B_, _Rhodymenia_ (with smaller algæ attached). _C_, _Grinnellia_. _D_, _Delesseria_. _A_, _B_, natural size; the others reduced one-half.] The fresh-water forms are not common, but may occasionally be met with in mill streams and other running water, attached to stones and woodwork, but are much inferior in size and beauty to the marine species. The red color is not so pronounced, and they are, as a rule, somewhat dull colored. [Illustration: FIG. 31.--Fresh-water red algæ. _A_, _Batrachospermum_, × about 12. _B_, a branch of the same, × 150. _C_, _Lemanea_, natural size.] The commonest genera are _Batrachospermum_ and _Lemanea_ (Fig. 31). CHAPTER VIII. SUB-KINGDOM III. FUNGI.