Forests and What They Give Us 521 



with the problem of public health. It is the duty of the Forest 

 Service to insist that sanitary conditions prevail in all camps on 

 the watersheds in order to guard against the pollution of the 

 water supply of the people who live in the cities and towns in 

 the valleys. 



Reforestation. The fact that our forests are disappearing, 

 in spite of all efforts to preserve them, makes it necessary that 

 steps be taken by the government to prevent this disaster. Refores- 

 tation is the remedy. In regard to this Col. Henry S. Graves, 

 when Chief of the United States Forest Service, said : "The ques- 

 tion of forest renewal and growth is one that can no longer be 

 ignored. It is not only of interest to the public, but it is of vital 

 concern to the owners of woodlands. I would have little concern 

 about the amount of timber used if we were growing new trees 

 in place of the old." 



Care of Trees. All persons are more or less interested in 

 trees. To few people, however, does it occur that the same con- 

 ditions or factors are necessary to the growth and develop- 

 ment of trees as are necessary to the growth and development 

 of man. They know that food, light, air, water and heat are 

 needful for their own growth and development, and that their 

 health would not be normal if any of these conditions were 

 permanently lacking. The same is true of trees, as of all plant 

 life. 



Different species of trees demand different kinds of climate. 

 Trees which grow naturally in the temperate zone are not able 

 to endure the hot sun of the equatorial latitudes, nor will they 

 live in the polar regions. Some of the largest known trees in the 

 world are found in the temperate zone, for example, the redwood 

 trees of California. There is a line in the colder regions of the 

 earth called the timber line beyond which trees cease to grow, 

 owing to the cold. 



Trees, like all forms of organic life, must have food in order 

 to carry on their life processes. Like other plants, they make 

 their own food, obtaining the raw materials from the air and 

 the soil. From the air they secure carbon dioxide and, from the 

 soil, water and food nutrients. These, under favorable conditions, 



