Seasonal Growths of Stems. 41 



beginning of the second. Do you see that the layer of 

 wood just below the bud would be very thin, and, therefore, 

 not easily seen ? * 



In the figure on page 40 the section at A shows two 

 seasonal growths, but at B, near the end of the first 

 growth, only one that of second season can be easily 

 made out. Is the pith as large in the growth of the last 

 season as in that of the first ? What change must take 

 place in the bark as the stem increases in thickness ? Do 

 you see any signs of its stretching ? Can it stretch enough 

 to cover the stem when it has grown to be two feet in 

 diameter ? Is the bark any thicker on the trunk of a 

 tree than it is on the twigs? If it grows in seasonal 

 layers, where is the youngest layer ? What becomes of 

 the oldest layer ? Sequoias live to be over two thousand 

 years old. Is any of the bark on a Sequoia that old? 

 Why do you think not ? 



Examine, this evening, bark on large trees or sticks or 

 on logs of wood. Count the layers of growth of the wood, 

 and thus estimate the age. Look at the end of a board and 



* In the diagram on page 40, the thickness of growth is represented as very 

 much greater in proportion to the length than is ever the case. It shows more 

 plainly than a real section that an ideal exogenous tree has a trunk made up of 

 a succession of elongated hollow cones, one over the other; the oldest one forming 

 the center for only a few feet at the base; the youngest enveloping all the others 

 from base to summit. This condition is nearly realized in coniferous trees. A 

 pile of hollow cones, all the same size, represents roughly the condition of a palm- 

 tree in which the trunk, made up on the outside of the bases of the equal cones, is 

 as large at the top as at the bottom or larger, if the younger growths were better 

 nourished. Only the upper (youngest) cone bears leaves, and these send fibers 

 down between the fibers of older growth for some distance. 



