THE 



139 



Tetraspores. In most of the Florideae the non-sexual reproductive 

 cells are tetraspores. These are formed in special cells, which may 

 either project as short, branches (Fig. 106) or are formed from an 

 inner cell of the thallus. Not infrequently the groups of tetraspo- 

 rangia are found upon special branches called Stichidia. Tetraspores 

 are wanting in some of the lower Florideae, e.g. Nemalion, or they 

 may be replaced by monospores (Batrachospermum) (Fig. 109), where 

 they are borne upon a special non-sexual plant, which was described 

 as another genus, Chantransia, under the impression that it was an 

 independent plant. In this case the sexual plant (Batrachospermum) 

 develops as a special branch from the Chantransia-form, somewhat as 

 the perfect Chara-plant arises from the pro-embryo. 



FIG. 108. A, Nemalion multifidum. (Natural size.) B, N. Andersonii. (Natural 

 size.) C, N. multifidum, branch with antheridia; 6 (X500). D, carpogonial 

 branch (X 500) ; t, trichogyne. E, young gonimoblast, or spore-fruit, sp. F, older 

 goniraoblast. 



Tetraspores may be formed by successive division of the mother- 

 cell, or by a simultaneous division of the protoplast after the nu- 

 cleus has divided into four. Sometimes (e.g. Corallina, Fig. 115) the 

 tetraspores are arranged in a row (zonate). 



Classification (Engler and Prantl, 9) 



As already stated, there is a good deal of variation in the charac- 

 ter of the sexual organs in the Florideae, and upon this the division 

 into orders is based. Four of these orders are usually recognized, 



