36 Rhodophycece 



The main argument for its inclusion in the Rhodophycese is 

 derived from the red colour of the chromatophores, whereas the 

 intercalary growth of the thallus and the absence of the pits 

 between the thallus-cells are points against its inclusion among 

 the Red Alga3. The so-called tetraspores of the Bangiaceae are 

 somewhat remarkable, the whole of the contents of a thallus-cell 

 going to form one unciliated, amoebiform spore. The sexual 

 process is also of a very reduced type, far removed even from that 

 of the simplest red Alga. The genus Bangia, which is a simple 

 filamentous form, occurs on the shores of the British Islands and 

 in the estuaries of the rivers, but it is not exactly a freshwater Alga. 



Order I. NEMALIONACEJE. 



The fertilized carpogonium gives origin directly to the gonimo- 

 blasts, which are developed in tufts. 



Family 1. HELMINTHOCLADIE^E. 



The thallus is filamentous, simple or branched, with the 

 secondary axes often arranged in whorls. The main axis may 

 consist of a single row of cells, or of a central cell-filament 

 surrounded by a cortical ring of smaller cell-filaments. The 

 gonimoblast is a short tuft of cell-filaments and the terminal cells 

 usually form the carpospores. When the terminal cell has shed 

 its carpospore, the supporting cell grows through into the old cell- 

 wall and produces a new spore-forming cell. There is no definite 

 wall to the cystocarp. 



Genus Batrachospermum Roth, 1797. This is an exclusively 

 freshwater genus with a wide distribution in temperate and 

 tropical climates. Most of the species prefer deep water in which 

 there is a slight current, but more rarely they are found attached 

 to stones in fast streams. They scarcely ever occur in stagnant 

 water, but are found frequently in bogs, usually at a point where 

 a spring rises. The thallus, which is of a blue-green colour and 

 enveloped in a thick coat of mucus, is remarkable for the great 

 beauty and symmetry of its branching; sometimes it reaches a 

 length of 16 20 cms. The plants are generally attached to 



