138 



BOTANY 



Affinities of Bangiales 



Aside from their color, and the absence of cilia in the reproductive 

 cells, the Bangiaceee recall certain Confervaceae, especially such forms 

 as Coleochaete, and it is by no means impossible that they connect 

 these with the higher Ehodophyceae, although this view must be con- 

 sidered for the present as nothing more than a conjecture. 



THE FLORIDE^} 



This is the largest group of Algse, and includes the greater number 

 of the common Seaweeds. 



X -, 



FIG. 107. A, Porphyra sp., plants growing upon a leaf of Phyllospadix ; x, young 

 plants. (Natural size.) B, cells from the thallus of P. vulgaris (x 450). C, an- 

 theridia (?) of P. vulgaris (X 250). D, Erythrotrichia ceramicola, showing fer- 

 tilization; sp, spermatium (X600). (D, after BERTHOLD.) 



The Plant-body. In a few forms, like Griffithsia, the plant is a 

 simple cell-row, but usually it is either a branching filament or a 

 broad thallus of some size. The Florideee, however, are inferior to 

 the Phaeophycese in size and in the complexity of their tissues. 



Apical Growth. With few exceptions the growth of the plant is 

 apical. Where it is a simple or branching filament the apical cell 

 is elongated, and has here segments cut off from it which undergo 

 no further divisions except as lateral branches are formed. In 

 others, such as Polysiphonia (Fig. Ill), the segments cut off from 

 the base of the conical apical cell here undergo further longitudinal 

 divisions, whereby the outer vertical cells are cut off from the axial 

 row of cells. In other forms, e.g. Champia (Fig. 116), there is a 

 group of initial cells at the apex of the thallus. 



