THE STEMS KINDS' AND FORMS; PRUNING 



' i /, 



57 



f 



- 



to keep out the germs and fungi. 

 A covering of sheet iron or tin may 

 keep out the rain, but it will not ex- 

 clude the germs of decay ; in fact, 

 it may provide the very moist con- 

 ditions that such germs need for 

 their growth. Deep holes in trees 

 should be treated by having all the 

 decayed parts removed down to the 

 clean wood, the surfaces painted or 



hollow trunk. filled with wax or cement. 



Stems and roots are living, and 

 they should not be wounded or 

 mutilated unnecessarily. Horses 

 should never be hitched to trees. 

 Supervision should be exercised 

 over persons who run telephone, 

 telegraph, and electric light wires, 

 to see that they do not mutilate 

 trees. Electric light wires and trol- 

 ley wires, when carelessly strung 

 or improperly insulated, may kill 

 trees (Fig. 67). 



SUGGESTIONS. Forms of stems. 



43. Are tne trunks of trees ever per- 

 fectly cylindrical? If not, what may 

 cause the irregularities ? Do trunks often 

 grow more on one side than" the other? 



44. Slit a rapidly growing limb, in spring, 

 with a knife blade, and watch the re- 

 sult during the season. 45. Consult the 

 woodpile, and observe the variations in 

 thickness of the annual rings, and espe- 

 cially of the same ring at different places 

 in the circumference. Cross-sections of 



FIG. 67. ELM TREE KILLED 

 BY A DIRECT CURRENT 

 FROM AN ELECTRIC 

 RAILROAD SYSTEM. 



