10 INTllODUCTION. 



damp places ; propagated by zoospores, coloured spores, 

 or tetraspores/' That portion of Algales, or Algse, of 

 which we mean more particularly to treat, are called 

 Sea-weeds, and, as their name implies, either grow in 

 the sea, or in places where they are, occasionally at least, 

 covered by the tide, washed by the waves, or moistened by 

 the spray. Though very different from each other in form, 

 colour, and general appearance, they are all similar, in so 

 far as they are composed of cellular tissue. They have not 

 continuous vessels like the phsenogamous plants, but consist 

 of cells differently arranged, or of gelatine, membrane, and 

 endochrome. They have no woody fibre, though there is 

 certainly the approach to it in appearance, as in the stems 

 of the Great Tangle. Lamouroux, indeed, tliinks that the 

 stem of Laminaria digitata is formed of four distinct parts, 

 analogous in situation, size, and organization to the epi- 

 dernm, harh, ivood, and 2nt7i of dicotyledonous plants. 

 That Marine Algse are not furnished with continuous vessels 

 like land-plants, is obvious from the well-known fact, that 

 if one part of a sea-plant is plunged in water, and the 

 remainder is exposed to the air, only what is in the water 

 remains fresh, the rest withers and becomes dry. And 

 in the same manner, if a dried specimen of Sea-weed is in 



