2 REPRODUCTION 



small and helpless. They go through a time of rapid 

 growth, which in humans we call childhood and youth. 

 After a time they become mature. Then, for a while, in 

 middle-life, they just about hold their own. Gradually 

 they show signs of old age, and decline, and later die. 

 This is true of practically all individuals of every kind of 

 plant and animal. Some of them have very short periods, 

 lasting a few days or weeks. Many plants go through all 

 these stages in a year. Still others require centuries or 

 even thousands of years to pass from the beginning to 

 the end of life. 



3. The Beginnings of Life. No one knows anything of 

 the actual beginnings of life on the earth, but we all have 

 seen the 3^oung bean seedling coming out of the seed, the 

 young tadpole just out of the egg, the young chicken just 

 hatched, or the young calf or puppy recently born. This 

 is not really the beginning of life for any one of these, 

 because if they had not been living before sprouting or 

 hatching or being born, these things would never have 

 happened to them. For our present purposes, however, 

 this may be taken as the beginning of the individual. In 

 some way there is in this young plant or animal all the 

 possibilities of the adult. If the conditions are right it 

 will go on day by day adjusting itself to these conditions 

 and will come to be pretty much what its parents were. 



4. Growth. Growth is increase in size. There may be 

 other changes in connection with growth, but growth is 

 just this and nothing more. Living things grow by taking 

 up water and stretching the old parts, or by taking up 

 foods of various kinds and building up some new parts. 

 Growth seems a rather simple thing. It is, however, very 

 complex, and it is quite different in different living things. 



In most higher plants the growth occurs only at certain 

 definite points. The growth is local. The growing points, 

 where the cells use the water and foods and thus grow 

 and form new cells, are usually at the tips of the twigs 



