266 ELEMENTARY SCIENCE 



find one much shorter and with only one good ear. Why 

 this difference ? 



It is certain that the difference between these two plants 

 is due either to a difference that they inherited from their 

 parents, or to differences in their surroundings as they 

 grew, or to both. In other words, all living things, animals 

 as well as plants, are what they are because of heredity 

 and environment. Heredity means what is inherited from 

 parents; environment means all the conditions that sur- 

 round an individual after birth. 



You have been studying the environment. You know 

 about the principal physical things (light, heat, air, etc.) 

 that affect life. Now you should think of plant life as a 

 great force in the world that is always trying to express 

 itself (in nutrition and reproduction) in the presence of an 

 environment that constantly acts upon it and affects it. 

 This has been going on for such a very long time that we 

 find plants usually quite well adjusted to their environ- 

 ments. This is to say, the shapes and structures of plants 

 seem to be a good deal determined by their surroundings. 

 We find very tough and hardy weeds growing in dry places, 

 while soft and tender plants are found in moist and shady 

 places. 



Forests are the highest expression of the plant kingdom, 

 and the most interesting study of plant life is the study of 

 the woods in the spring when the leaves are coming out and 

 the early spring flowers are found all over the floor of the 

 forest. If you were to go into the woods some fine day in 

 late April or early May, you might find the "spring flora" 

 at its best. Then you could stop to think what the " woods" 

 really means. In level country the woods usually means 

 great age of the topography. The trees on dry bluffs and 



