198 DISF.ASl-: I\ PLANTS. 



across the wound, a layer of wood will be formed 

 all round the intact part of the stem, from lip to lip 

 of the cut tissues during the first year ; then a 

 second annual layer outside this will be formed 

 during the second year, but extending further 

 over the edges of the wound, and nearly complete, 

 because the cambium has now crept further across 

 the wounded surface to meet the opposite lip of 

 cambium ; and during the third year, when the 

 cambium has once more become continuous over 

 the face of the wound, the annual wood layer will 

 be complete. But, of course, this last layer covers 

 in the edges of the two previously developed 

 incomplete wood-layers as well as the exposed and 

 brown, dry, or rotten dead face of the wood. It 

 also covers up the trapped-in brown cork and 

 any debris that accumulated in the wound, and 

 this " blemish/' though buried deeper and deeper 

 in the wood during succeeding annual deposits of 

 wood-layers, always remains to remind us of the 

 existence of the wound, the date of which can be 

 fixed at any future time by counting the annual 

 rings developed subsequently to its formation. 

 Obviously, also, the deficiency of wood at this 

 place makes itself visible on the outside by a 

 depression. 



Cuttings. When a cutting of Pelargonium, 

 Willow, or other plant is made, we have a typical 

 knife-wound, the behaviour of which is very in- 

 structive in illustration of plant-surgery, and may 

 be most easily seen by keeping it in damp air 

 instead of plunging it into sand or soil. 



