CHAPTER II. 



FIG. 42. Closterium 

 lunula, c cytoplasm; 

 n, nucleus; w, cell 

 wall ; r, chlorophyl - 

 bearing protoplasm ; 

 p, p y r e n o i d ; v, 

 vacuole. 



THE SIMPLER ORGANISMS. 



To understand the complex phenomena of life we must 

 seek their simpler expressions. The relations between the 

 higher and more familiar forms of life are very intricate. 

 The bodies of such plants and animals as we have been ob- 

 serving are highly organized composed of many parts 

 having special functions. How shall we learn what are the 

 primary parts and functions of living things? It will help 

 us to distinguish essentials 

 if our first quest be made 

 among organisms of lowly 

 structure. The'simpler plants 

 and animals live in the water. 

 We have already learned that 

 the main gatherers of food material for the living 

 world are green plants. The simplest green 

 plants are the algae ; so with these we will begin. 



SOME TYPICAL ALGAE. 



When we learn to recognize them we can 

 hardly look into the water anywhere without seeing algae. 

 They float in green masses upon the surface ; they hang in 

 graceful drapery of verdure on submerged branches; they 

 drip in globules of gelatine from twigs that are lifted out of 

 the water : they rise from the bottom ; they lie amid the 

 silt ; they trail across the rocks that are swept by the cata- 

 ract ; they cling to wave-beaten piers, and boulders ; they 

 are free-swimming, and come in our water supply ; and they 

 grow and flourish in the bottle of clear water that is long left 



