90 



wide strips whenever possible. A strip of 8 rods is always possible. 

 The trees upon this strip would all be counted, but on a very wide 

 strip the diameters of only a portion might be tallied. The num- 

 ber tallied should always be equivalent to the stand on a 4-rod 

 strip. Heights would be tallied with the diameter, or, if it is 

 sufficiently accurate, may be averaged. Where it is more con- 

 venient and time must be saved the system of using plots is best, 

 either circular or rectangular, and spaced at definite distances. 

 Here either the trees may be counted or the diameters of all of 

 the trees on the plots tallied. The selection of sample plots here 

 and there should be left only to persons of exceptionally good 

 judgment and long training. 



Only the most experienced timber cruisers may dipense with 

 both volume tables and a tally of the sizes of the trees, and obtain 

 their results directly by counting and by averaging the contents 

 of the logs or the trees in the stand. 



GROWTH OF TREES. 



Since there is a marked tendency among timber-land "owners to 

 cut their timber with an eye to the future, some knowledge of the 

 growth of forest trees becomes important. 



Trees grow by adding each year a layer of wood underneath the 

 bark. Since each year contains only one growing season and the 

 spring and summer part of this layer are not alike, each year's 

 growth, layer, or "annual ring" usually is distinguishable. The 

 central fact of tree growth is that each ring means a year. The 

 exceptions to this are not important enough to merit notice here. 



DIAMETER GROWTH. 



Some trees grow so slowly that a hand lens is necessary to 

 clearly distinguish the rings, others may have rings a half inch in 

 width. In any case, a little practice improves the ability to note 

 all the rings. 



To find the age of a felled tree at any section, then, requires 

 only the accurate counting of the rings. The total age of the tree 

 is shown by the total number of rings at the ground; or the total' 

 number of rings on the stump plus the number of years required 



