38 



FIRST STUDIES IN PLANT LIFE 



20 (1), outside of the pith a ring of wood ; and, outside 

 of all, the bark. On the outside of the bark you 



find a thin skin which 

 afterwards thickens; below 

 this there is the green 

 layer of the bark, and still 

 farther in we have the 

 inner bark. 



A two-year old stem. 

 Take now a two-year old 

 stem, and you will see (1) 

 the pith, (2) the wood of 

 the first year, (3) the new 

 wood, (4) the bark. A 

 three-year old stem will 

 shew (1) the pith, (2) the 

 wood of the first year, (3) the wood of the second year, 

 (4) the new wood, and (5) the bark. You can see now 

 how the age of a tree can be told from these annual 



Oak-stem cut across to show the 

 annual rings. The new wood 

 (sap-wood) is just below the bark. 

 The rays running from pith to 

 bark form the silver grain. 



'FI&20 



One-year old (1), two-year old (2), and 

 three-year old (3) shoots. In No. 3 the 

 inner ring of bark is the new bark, 

 and the third ring of wood, counting 

 from the pith, is the sap-wood (new 

 wood.) 



One-year old stem, show- 

 ing the pith and the pith- 

 rays (silver gi-ain). 



