COLOSSAL ALG^. 89 



by the same colouring matter — the substance called leaf- 

 green, or chlorophyll — which colours the leaves of all the 

 higher plants. 



To this class belong, besides a great number of low 

 marine Algae, most of the Algge of fresh water, the 

 common water hair-weeds, or Confervse, the green sKme- 

 balls, or Gloeosphserse, the bright green water-lettuce, or 

 Ulva, which resembles a very thin and long lettuce leaf, 

 and also numerous small microscopic algse, dense masses of 

 which form a light green shiny covering to all sorts of 

 objects lying in water — wood, stones, etc. 



These forms, however, rise above the simple primary Algae 

 in the composition and differentiation of their body. As 

 the green Algae, like the primaeval Algae, mostly possess a 

 very soft body, they are but rarely capable of being petrified. 

 However, it 'can scarcely be doubted that this class of Algae 

 — which was the first to develop out of the preceding 

 one — most extensively and variously peopled the fresh and 

 salt waters of the earth in early times. 



In the third class, that of the Brown Tangles (Phaeo- 

 jihyceae), or Black Algce (Fucoideae), the branch of the Algae 

 attains its highest stage of development, at least in regard 

 to size and body. The characteristic colour of the Fucoid 

 is more or less dark brown, sometimes tending more to 

 an olive green or yellowish green, sometimes moi-e to a 

 brownish red or black colour. 



Among these are the largest of all Algae, which are at 

 the same time the longest of all plants, namely, the 

 colossal giant Alga?, amongst which the Macrocystis 

 pyrifera, on the coast of California, attains a length of 

 400 feet. Also, among our indigenous Algae, the largest 



