HEALING OF WOUNDS ON WOODY STEMS 1 33 



Ex. 61. — Examine boards of different kinds of wood : observe the arrange- 

 ment of the annual rings on the sides and ends. Try and determine whether 

 the boards were cut from near the middle or the outside of the trees. 

 Observe also the distribulion and size of the knots. 



► Ex. 62. — Cut blocks as in Fig. 62 of various kinds of common timber. 

 Examine with the naked eye and with a pocket lens : notice the presence 



Fig. 6z. — Diagram showing transverse, radial, and tangential 

 views of a block of wood from a tree five years old. p Pith or 

 medulla; r' primary, r" secondary medullary rays; j zone of 

 porous spring-wood. 



or absence of wide vessels in the spring zone of the annual ring, and the 

 number, width and other characters of the medullary rays as seen in transverse 

 and longitudinal sections. 



Ex. 63. — Notice the well-marked heart-wood in transverse sections of 

 larch, laburnum and other trees ; test whether the splint-wood is harder or 

 softer than the heart-wood. 



Ex. 64. — Notice the development of callus at the edge of the wound where 

 a thickish branch has been cut off an apple, pear or other tree. 



Ex. 65. — Make transverse sections through a young stem of a black 

 currant about mid-summer, mount them in a drop of water or glycerine. 



Sketch the parts as seen with a low power ; afterwards use a high power, 

 and make drawings of small portions of the epidermis, cortex, cork, phellogen, 

 bast, cambium, wood pith and medullary rays. 



