ALGJ3, OR SEA-WEEDS. .39 



istence, with food throughout their dreary winter; its vegetation 

 not being checked by the snow beneath which it grows. A species 

 of Lichen growing on the rocks of the Arctic regions of North 

 America, has afforded subsistence for many days, to some of the 

 adventurous explorers of that desolate country, when other pro- 

 visions could not be obtained. 



40. The group of Algae, or Sea-weeds, includes the very 

 lowest forms of vegetable organization ; but it also comprehends 

 some plants whose structure possesses great complexity. The 

 Algae may be considered as Lichens formed to exist in water ; 

 their general structure, and the arrangement of their parts, being: 

 much alike. The hard scaly crust of the Lichens, formed under 

 the influence of the sun and air, and never attaining any great 

 extent, seems to bear a remarkable contrast with the immense 

 leaf-like expansions, composed of soft, easily decomposed tissue, 

 presented by the Algae ; yet wherever any of the former group 

 inhabit damp shady places, their character much approaches to 

 that of the latter ; and in regard to some plants, it is difficult to 

 fix the group to which they belong. Although the term Sea- 

 weed is that usually considered equivalent to Algee, it should 

 be understood that the class includes many 

 species, which are inhabitants of fresh water. 

 Of this kind are the Confervas^ the long green 

 hair-like filaments of which are almost con- 

 stantly found attached to stones, at the sides or 

 bottom of running streams. These are among 

 the simplest forms of vegetation. Each fila- 

 ment consists of a single row of minute cells 

 or vesicles, attached to each other end to end. 

 Every one of these vesicles is capable of growing 

 by itself, and of reproducing its kind ; for at a 

 certain period a minute orifice appears in its 

 walls, from which issue forth some of the little 

 green particles it contains ; and these become 

 the germs of new plants of the same descrip- 



/f ^, v FlG. 10. CONKERV.K, 



tion (Chap. XII.). with separate filament 



41 . The higher kinds of Alga inhabit Sea- ma & nified - 





