364 EXPLOEATOEY NOTICES FOE AUGUST. 



purple, rarely brown-red or greenish-red. III. Cklo- 

 rospermeG or Confervales plants green, rarely a livid 

 purple. He remarks that the green Algae are the 

 simplest in structure, that their lowest members are 

 the least compound of all vegetables, some consisting 

 of a single cell, others of a string of cells linked toge- 

 ther end to end ; and that the most developed of this 

 group are not on a par with the least complex of 

 either of the other groups. A good idea of the green 

 Algae may be obtained from the common curled gut- 

 ling (EnteromorpJia intestmalis), often nearly filling 

 stagnant ponds with its floating pod-like fronds. 

 These, at first fixed by a minute root, become detached 

 and floating, and thus inflated, and of a lively green, 

 curl in all directions about the pool they inhabit, 

 presenting the curious aspect of the intestines of 

 some destroyed animal. Finally they fade and become 

 bleached nearly white. The Confervce, also comprised 

 in the green Algse, chiefly inhabit fresh water in all 

 parts of the world, and form the bright green glossy 

 threads that float on the surface of ponds and ditches. 

 " "When young," says Dr. HAEVET, " the filaments 

 lie at the bottom of the pool, but, as they approach 

 maturity, they float to the surface, where they often 

 lie so thickly as to retain within their meshes large 

 bubbles of air, which they have disengaged during the 

 progress of vegetation, and which is in great part 

 oxygen. "When shallow water lies for some weeks in 

 summer on the surface of flat land, it often becomes 

 completely filled with the threads of these plants, 

 which, by their vegetation, counteract the evil effects 

 which the decay of other vegetables under the water 

 would otherwise dispense, and on the clearing off of 



