THE BREATHINGS OF A TREE. 

 HOAV THE TREE BREATHES. 



15 



Besides giving out oxygen in assimilation, trees also 

 take in oxygen from the air through their leaves, and 

 through the minute openings in the bark called lenticels, 

 such as the oblong raised spots or marks on the young 



FIG. 13. Bark of the Western Yellow 

 Fm.l2.-Woodandbark Fine ' Outer 8urface Bowing the 



of the Western Yellow scale * lnade b y tbe "essive layers 



Pine. The cnt is a of cork cambium, 



cross section and . 



have been hor- branches of Birch and Cherry and 

 as the speci- many other trees. All plants, like 

 all animals, breathe; and plants, like 

 breathe in oxygen and 

 breathe out carbonic acid gas. This 

 in the bark, aUhebot- process of respiration or the breathing 



^pi f ,^ Ch lenUcel8 of the tree goes on both day and nigllt ' 

 but it is far less active than assimila- 

 tion, which takes place only in the light. Consequently 

 more carbonic acid gas is taken into the tree than is 

 given out, and the surplus carbon remains to be used 

 in growing. 



men stood in the tree. 



Besides the division 



of the bark into scales animals, 



this picture shows 



twoof thedeepcracks 



