364 ELEMENTS OF GENERAL SCIENCE 



growth, and not reproduction. Cell division results in repro- 

 duction in the case of one-celled animals and plants, as in 

 the bacteria. 



372. Reproduction of the yeast plant. The yeast plant con- 

 sists of a single spherical or oblong cell (fig. 168). It has a 

 simple wall, within which are the living substances that con- 

 stitute the protoplasm. Yeasts get their food material from 

 the solutions in which sugar is dissolved, and in doing so 

 partially decompose the sugar; this partial decomposition 

 results in the production of alcohol. But when nutrition is 

 abundant the yeast plants enlarge and soon begin the pro- 

 duction of new plants. First 

 there may be noted a small, 

 budlike outgrowth on one 

 side of the parent plant 

 This bud enlarges for a time 

 and finally becomes sepa- 



Yeast plants rated. The separated bud is a 



a, a plant from which a bud has begun to new yeast plant, and after a 



grow ; b and c plants each of which has brf f rf d f Rrowth ifc may 

 two buds. Greatly enlarged & * 



repeat the budding process 



by which it came into existence. Indeed, sometimes a large 

 bud, even before it becomes separated from the parent, begins 

 to form a small bud for the production of the third plant in 

 the series. 



Budding represents one of the simplest kinds of repro- 

 duction. This is known as vegetative reproduction, because 

 reproduction is accomplished by means of the ordinary nutri- 

 tive, or growing, part of the plant. Many simple animals are 

 reproduced in a similar way. 



373. Reproduction of pond scum. Almost everyone has 

 observed the common green " pond scum " floating on the 

 surface of water or submerged. Some of this consists of 

 plants which are very beautiful when seen under the micro- 

 scope. They are silky threads composed of large cells 



