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CHAPTER VII. 



(ALGA, SEA- WEED). 



THE plants belonging to the Class Algae grow in 

 water, either in that of the sea or in fresh water ; a 

 few of them, however, being found on damp earth, 

 damp walls, &c. The marine Algae are commonly 

 known as sea-weeds ; but the fresh- water Algae gene- 

 rally receive but little popular notice, forming, as they 

 do, slimy masses or strata, of a green or brownish, 

 sometimes red, colour. 



Algae are of simple structure, consisting entirely of 

 cells ; in some these are single, in others, united end 

 to end, to form threads or filaments, or grouped into 

 a leaf-like expansion, or collected few together into a 

 little spherical group or a flat plate. They possess 

 none of the fibres, vessels, or ducts of the higher 

 plants, although some long and slender cells, existing 

 in the stalks of the fronds of the larger kinds, bear 

 considerable resemblance to woody fibre. They ex- 

 hibit no distinction of stem and leaf, but consist of 

 fronds representing the stem and leaf combined and 

 undistinguishable. And the term frond must be un- 

 derstood to signify the separate parts arising from 

 the point of attachment when they are fixed ; and in 

 the case of those which are unattached or free, the 

 entire plant is called a frond. 



The Algae are divided into three Orders, viz. the 

 Fucoid'eae or olive-coloured Algae, the Florid' eae or 

 red, and the Confervoid'eae or green Algae. 



FUCOID'EAE, Fucoid Algae, or Melanospor'eae (yu-eXa?, 

 black or dark). The plants composing this order 

 form our largest sea- weeds, and are found everywhere 



