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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 may be 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 rhodopbyll. 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 Floridea3 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 RhodophyceaD may be divided into two families : 



1. BANGIOIDE^;. 



2. FLORIDEJE. 



Family 1. Bangioidese,. 



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 (.Bawgrta-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. 



