FORMATION OP WOOD 259 



again, many other trees besides the conifers are 

 known as softwoods. 



Of the Angiosperms, the Dicotyledons alone 

 need be considered from a timber-bearing point 

 of view. They bear broad leaves, for the most 

 part and, like the Gymnosperms, their stems 

 increase in thickness omng to successive annual 

 growths of wood. These yearly additions of 

 wood are clearly seen as rings, known by the 

 name of annual rings (Pig. 81), in any cross 

 section of a dicotyledonous tree. 



We may mention here, as we shall explain 

 later, that these rings may be formed other than 

 annually under exceptional circumstances. There 

 is good reason for the continued growth of the 

 dicotyledonous stem as compared with the 

 almost stationary (as far as girth is concerned) 

 monocotyledonous stem. We have stated that 

 the wood supports the stem, but it does more. 

 Through the tissues of the wood, water and 

 dissolved raw food material taken up by the 

 roots passes to the leaves, then to be elaborated 

 and converted into complex substances such as 

 starch and sugar, which serve to nourish the tree 

 and to feed the growing points. The greater 

 part of the moisture which finds its way to 

 the leaves is given off, in the form of vapour, 

 into the air. The stem also acts as a store- 

 house, much of the manufactured food being 



