ASEXUAL REPRODUCTION 317 



Asexual Reproduction in the Alg^e.^ There are 

 many plants of much simpler organization than the 

 Flowering Plants, the only ones with which most persons 

 are at all familiar. The lowest and simplest plants be- 

 long to the Algae. These plants are typically aquatic; 

 they have simple bodies, of no very high degree of spe- 

 cialization, and simple methods of reproduction. Some 

 of the lowest do not have any sexual method at all. 

 Two or three examples will make this clear. 



Oscillatoria (Fig. 78) is an alga of blue-green color 

 found in shallow temporary pools^ in lakes and streams of 

 stagnant water, about the outlets of sewers and other 

 similar places where the water contains considerable 

 amounts of filth. Its habits of life are, however, 

 not the immediately interesting subject, but its method 

 of reproduction. As the illustrations show, a single 

 plant consists of a simple row or filament of short 

 cylindrical cells placed with their flat surfaces in 

 contact. A careful inspection will fail to reveal any 

 essential difference among the cells, except that the 

 terminal ones have their free end rounded out in- 

 stead of flat. Any cell or group of cells may be detached 

 from the others without making any difference in their 

 development. Each one goes on manufacturing its food 

 and growing independently of the rest. As each cell 

 grows it reaches a point when division occurs, making 

 two out of it. This increases the length of the filament. 

 Any disturbance, such as frequently occurs in the water 

 in which it grows, may break the filament into two or 

 more pieces. Obviously in this plant there is no real 

 distinction between growth and reproduction. Any cell 

 division may accomplish either or both. If the pond 

 'dries up the plants are dried also. Fortunately the pro- 

 toplasm is able to endure such treatment without killing 

 all of the cells, though most of them do not survive. 

 Those which do live need only that the necessary heat, 

 light, and moisture be again furnished them to begin 



