CHYPTOGAMOUS OK FLOWEKLESS PLANTS. 509 



sporales, in rows, like tlic beads of a necklace (Fig. 93), which, 

 separating, become the rudiments of new plants. 



980. Ord. Alga; (Seaweeds). Tliis vast order consists of aquatic 

 plants, for the most part strictly so, but some grow in humid ter- 

 restrial situations. The highest forms are the proper Seaweeds 

 ( Wrack, Tang, Dulse, Tangle, &c.) ; " some of which have stems ex- 

 ceeding in length (although not in diameter) the trunks of the tallest 

 forest-trees, while others have leaves (fronds) which rival in expan- 

 sion those of the Palm." " Others again are so minute as to be 

 wholly invisible, except in masses, to the naked eye, and require the 

 highest powers of our microscopes to ascertain their form and struc- 

 ture." Some have the distinction of stems and fronds ; others show 

 simple or branching solid stems only ; and others flat foliaceous ex- 

 pansions alone (Fig. 95), either green, olive, or rose-red in hue. 

 From these we descend by successive gi'adations to simple or 

 branching series of cells placed end to end, such as the green Con- 

 fervas of our pools, and many marine forms : we meet with congeries 

 of such cells capable of spontaneous disarticulation, each joint of 

 which becomes a new plant, so that the organs of vegetation and of 

 fructification become at length perfectly identical, both reduced to 

 mere cells ; and finally, as the last and lowest term of possible vege- 

 tation, we have the plant reduced to a single cell, giving rise to new 

 ones in its interior, each of which becomes an independent plant 

 (Fig, 79 - 83, 18 - 22). Our Algse should be studied by the aid of 

 the 'admirable Nereis Boreali-Americana, or History of the Marine 

 Alga of North America, by Professor Harvey, published by the 

 Smithsonian Institution. For the fresh-water species we have no 

 American work. The main divisions of Algse are into the following 

 suborders. 



981. Subord, MelanOSpermea), or FucaceEB, the Olive-green Seaweeds; 

 having dark-colored spores and generally an olive-green color, such 

 as the common Rockweed, Gulfweed, &c. The fertilization of these 

 spores has already been described (661). 



982. Subord, Rhudospcrmese, or Floridea;, the Rose^ed Seaweeds, so 

 called from their prevailing color. These, the most beautiful of 

 AlgEe (including the Dulse, Laver, &c.) have two kinds of spores ; 

 one large, simple, and superficial ; the others dispersed through the 

 interior of the frond, and formed four together in a mother cell. 



983. Subord.. ChlorOSpemCBE, the Bright-green Algm, the spores and 

 the vegetation of which are generally of a lively gi-een hue, are more 



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