BANG10IDE.E. 77 



Class 10. Rhodophyceae (Red Seaweeds). 



The plants comprised in this class are multicellular ; they are 

 simple or branched filaments, or expansions consisting of 1 to 

 several layers of cells; the thallus maybe differentiated (as in 

 many Floridece), to resemble stem, root, and leaf. The cells con- 

 tain a distinctly differentiated nucleus (sometimes several), and 

 distinct chromatophores, coloured by rhodophyll. The chloro- 

 phyll of the chromatophores is generally masked by a red colour- 

 ing matter (phycoerythrin), which may be extracted in cold, fresh 

 water ; or rarely by phycocyan. Pyrenoids occur in some. Starch 

 is never formed in the chromatophores themselves, but a modifi- 

 cation Floridea? starch may be found in the colourless proto- 

 plasm. Asexual reproduction by motile or motionless spores 

 (tetraspores) which are devoid of cilia and of cell-wall. Swarm- 

 spores are never found. 



Sexual reproduction is wanting, or takes place by the coales- 

 cence of a spermatium and a more or less developed female cell. 

 The spermatia are naked masses of protoplasm, devoid of cilia and 

 chromatophores. The female cell (carpogonium) is enclosed by a 

 cell-wall, and after fertilisation forms a number of spores, either 

 with or without cell-walls (carpospores), which grow into new 

 individuals. 



The Rhodophycea3 may be divided into two families : 

 1. BANGIOIDE.E. 



Family 1. Bangioidea.. 



The thallus consists of a branched or unbranched cell-filament, 

 formed of a single row or of many rows of cells, or of an expan- 

 sion, one or two layers of cells in thickness, but without conspic- 

 uous pores for the intercommunication of the cells. The growth of 

 the thallus is chiefly intercalary. The star-like chromatophores 

 contain chlorophyll and are coloured blue-green with phycocyan, 

 or reddish with phycoerythrin ; all these colouring' matters are 

 occasionally found in the same cell (Bangia-species). Asexual 

 reproduction by tetraspores, without cilia, but capable of amoeboid 

 movements. 



Sexual reproduction is wanting, or takes place by the coalescence 

 of a spermatium with a carpogonium, which is only slightly differ- 

 entiated from the vegetative cells, and is devoid of a trichogyne. 



