478 Introduction to the Study of Science 



vegetables, and fruit trees, only a few stray plants of a different 

 kind, called weeds, will be found, for these are kept out by the 

 plow and cultivator. 



In nature which at first seems to be fair and peaceful in all 

 its ways, there is always a life-and-death struggle among all 

 plants for light, food materials, and water ; and in this struggle 

 many are crowded out and perish. The supply of light, food 

 materials, and the space for growth are insufficient for all plants 

 that start growth ; as a result comparatively few survive. 



Exercise. Select a small plot of ground, which may be left un- 

 disturbed all summer, and protect it by a light frame of lath about 

 fourteen inches square, pressed firmly into the ground. Do this early 

 in the spring just when plants are emerging from the ground. Every 

 plant appearing within the frame and for a distance of six inches on 

 all sides should be allowed to grow as it will. From time to time 

 count and record the number of individuals and kinds of plants. 

 Study the characteristics of those that seem to have any advantage 

 over others in the struggle. 



Observe and keep a record of the chief conditions to which the 

 plants must be adapted at different times during the summer. It 

 may be found that those survive which are most resistant to climatic 

 extremes, such as prolonged dryness, intense heat, strong wind, driv- 

 ing rain, and to disease, insect and other enemies, and are also best 

 fitted to secure necessary light, food, and water. Whether large and 

 symmetrically developed, or small, stunted, and unshapely, the sur- 

 vivors possess the qualities necessary to win out in the struggle for 

 existence. 



Note, also, how plants that survive and mature are fitted to secure 

 the propagation of their kind ; that they are very prolific, producing 

 seeds enough to plant a small field, perhaps a hundred for one that 

 will survive at the end of the following season. 



In any field or forest, along roadside, river, and fences, on 

 mountain ranges and plateaus, on the prairies and the deserts, 

 there are plants peculiarly adapted to the places where they 

 grow and able to win out in the natural struggle for existence. 

 Trees struggle for light and food materials in the forest, and 

 those growing rapidly survive, while the slow-growing starve 

 and eventually perish. Beneath the trees many different 



