MANUAL OF NATURAL HISTORY. 535 



III. ORDER. ALGALS (Algales). 



Living in water or very damp places ; nourished 

 through their whole surface by the medium in which 

 they vegetate ; propagated by zoospores, coloured 

 spores, or tetraspores. 



1. FAMILY. Stone-ivorts (Characese). Aquatic, sub- 



mersed ; odour fetid ; colour dull-green ; a 

 central stem or axis, often encrusted with 

 carbonate of lime ; branches in regular whorls, 

 symmetrical, tubular ; organs of reproduction 

 round brick-red globules, and axillary oval 

 nucules, the latter containing starch-granules. 

 Occur in salt-water, or in stagnant fresh- water 

 in all parts of the world, but more abundantly 

 in temperate climes. 



2. FAMILY. Rose-tangles (Ceramiacese). Sea-weeds ; 



rose-coloured or purple ; bodies cellular or 

 tubular, unsymmetrical ; reproduction by 

 tetraspores enclosed within a transparent pe- 

 rispore, and collected in bodies of different 

 forms. All marine plants, chiefly inhabiting 

 from 35 to 48 N. lat., diminishing towards 

 the equator and the pole ; rare in the South- 

 ern Hemisphere. Several gelatinous species 

 are employed as food, as Chondrus crispus 

 or Carrageen ; Rhodomenia palmata, or dulse ; 

 and Laurentia pinnatifida, or pepper-dulse ; 

 Plocaria tenax yields a matter used by the 

 Chinese as glue and varnish. 



3. FAMILY. Sea-weeds (Fucacese). Bodies cellular 



