284 MINNESOTA STATE HORTICULTURAL SOCIETY. 



is an essential factor in the food of plants. For obtaining this 

 gas fhe under side of leaves is provided with valves of delicate 

 mechanism, and so numerous that by actual count 25,000 on an 

 average are found on each square inch of surface. This would 

 give 100,000 or more of these valves to every ordinary leaf. With 

 out estimating the number of leaves on a tree, these figures will 

 give an idea of the extent of their purifying power. For cool- 

 ing the hot summer air they are no less valuable. The moisture 

 absorbed by the roots is transferred to the leaves, and a portion 

 of it exhaled through the small valves. This exhaling power 

 of leaves has been carefully investigated, and the best authorities 

 report that it is sufficient to have a perceptible influence in af- 

 fecting the humidity of the atmosphere and cooling the air. We 

 all know how refreshing is the air in the woods after a walk 

 or drive in the open country, and the comfort of shade in a 

 city street on a hot summer day. 



Several of the states, recognizing the value of roadside trees, 

 offer bounties to encourage planting them. 



One of the great needs of Minnesota is better roads, and 

 it is to be hoped that in the near future the state will follow 

 the example of the eastern states and macadamize the most impor- 

 tant thoroughfares and line them with trees. 



In the last report of the highway commissioner I find the 

 following: "Trees break the wind and also assist in keeping 

 the road in good condition. Especially are trees planted on long 

 stretches of macadam roads where they occupy an exposed 

 position. The trees afford shade and thus allow the moisture 

 to remain in the road without any artificial assistance in the way 

 of sprinkling. This in time will remove the necessity of sprink- 

 ling the roads, as it has been found that macadam roads protect- 

 ed by trees retain their shape longer and do not show wear or 

 break up as quickly as do roads not so protected." 

 -". I have dealt with this subject from the practical standpoint, 

 but I cannot close without referring to its aesthetic side. 



There are but few people in the world who do not admire 

 noble trees on streets or country roads, and wherever they are 

 found, such thoroughfares are the favorite drives. 



The man who plants trees is not only a public benefactor, 

 he, besides, ministers to his own well being, physical, mental 

 and spiritual. He deserves credit for altruistic work, and he dis- 

 plays good judgment in securing contentment for himself, there- 

 by affording a double motive for his endeavors. Honor and hap- 

 piness will be his reward. 



