64 DA VET" s PRIMER 



" How does the carbon get into the leaves? " 



Good question, Jacob. As you advance in your 

 studies and take up botany, you will, I think, become 

 wonderfully interested. On the under part of the leaf 

 are little openings, called stomata (stoma, singular). 

 They are so small and close together that there are at 

 times millions of them on a single leaf! Hard to be- 

 lieve, is it not? It is through these little holes that the 

 water escapes, and in through them the air, carrying 

 carbonic acid gas, assists in making material which, as 

 was said, is called "cambium." 



"What course does this cambium take to build up 

 the different parts of the tree? " 



You would make a good botanist Clara ; your in- 

 quiring mind would lead you to find out causes. Now, 

 listen : the sap is gathered, or pumped up by the roots 

 and sent up through the cells, in the wood, proper; and 

 the nearer it is to the outside the more open -the cells 

 and the more freely it flows. After it has been to the 

 leaf and undergone a change, then it returns down out- 

 side the last year's wood, between that and the bark 

 and, as it travels, the protoplasm works, building cell 

 upon cell and layer upon layer. This interesting work 

 continues down and out into the roots, clear out to the 

 tinniest little worker. As the tree grows the cells are 

 built, as was before stated, much like the "mains" of 

 a water-works system. Suppose some one should 

 make the mistake of cutting off one of those large main 



