22 



J^ESSOIfS WITH PLANTS 



fall of snow broke it off as we now see it. As 

 soon as it died, it became a menace to the tree, 

 for the rot in its tissues might extend into the 

 trunk. The tree made an efEort to cover it up. 

 The tissue piled higher and higher about, its base, 



Fig. 20. 

 Knot in a hemlock log. 



Fig. 21. 

 Improper cutting of a limb. 



reaching for the end of the wound. The limb was 

 eaten away by decay, and became smaller and 

 smaller in diameter, leaving a cup-like ring about 

 its base. Finally it broke off, and a knot-hole 

 was left. Such a knot-hole is seen in Fig. 19. 

 Knot-holes on the bodies of trees, then, are the 

 cavities left by dead and decaying limbs. 



