INTRODUCTION. 



the trees protect it so that it remains soft. The mixture of 

 leaves and loose top-soil forms what is known as humis. Humis 

 receives and protects young seeds, and assists the small hair- 

 roots which cannot so easily penetrate hardened soil. 



Humis also acts by equalizing the flow of streams. Rain 

 rolls quickly from sun-baked or otherwise compacted soil, but 

 humis permits the rain drops to pass through into the protected 

 sponge below and then reduces evaporation from this sponge. 

 It is not known that forests influence rain-fall but their value 

 in regulating stream-flow is beyond estimate. 



Forestry includes the planting and management of forests 

 and is agriculture as distinguished from lumbering. Forests are 

 not destroyed for immediate profit but are maintained so as to 

 secure recurring crops of matured and desirable trees. Appro- 

 priate species are planted, humis is preserved, fire risks are les- 

 sened and saplings are planted as the riper trees are cut down. 

 Forestry calls for small profits but these continue from year to year, 

 whereas the lumberman receives larger profits once and finally. 



The size and character of 

 the trunk, and the range, local- 

 ity, or distribution of the tree, 

 have much to do with the 

 utility of the wood, since large 

 or perfect timbers cannot be 

 derived from species character- 

 ized by small or crooked trees, 

 and since wood is always more 

 used if it is widely distributed 

 so as to be easily available.* 



FIG. i. SOME WOOD ELEMENTS. 



Wood is made up of cell- 

 structures; as, the true fibre, 

 which originates from several 



cells; the tracheid (tra-ke-id), which originates from one; the 

 vessel, which is a short, wide tube joined vertically end to end 



* Fossils show that many species covered wider ranges than at present. 



