THE RED ALG^. 51 



If alcoholic material is used, it may be mounted for exami- 

 nation either in water or very dilute glycerine. 



The plant is composed of much-branched, slender filaments, closely 

 resembling Cladophora in structure, but with smaller cells (Fig. 29, 

 S). The non- sexual reproduction is by means of special spores, which 

 from being formed in groups of four, are known as tetraspores. In the 

 species under consideration the mother cell of the tetraspores arises as a 

 small bud near the upper end of one of the ordinary cells (Fig. 29, G i). 

 This bud rapidly increases in size, assuming an oval form, and becoming 

 cut off from the cell of the stem (Fig. 29, C n). The contents now 

 divide into four equal parts, arranged like the quadrants of a sphere. 

 When ripe, the wall of the mother cell gives way, and the four spores 

 escape into the water and give rise to new plants. These spores, it will 

 be noticed, differ in one important particular from corresponding spores 

 in most algae, in being unprovided with cilia, and incapable of spontaneous 

 movement. 



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, Z), 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 move- 

 ment of the water to convey it to the neighborhood of the procarp. Occa- 

 sionally one of these spermatozoids may be found attached to the tri- 

 chogyne, 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 op- 

 posite sides of the filament grow rapidly and develop into large, irregular 

 masses of spores (Fig. 29, D in, iv). 



