ANATOMY. 7 



fibres are much thinner-walled than true wood-fibres. The more 

 the latter predominate, the harder and firmer the wood. In 

 oakwood, for instance, thin-walled tracheids are chiefly formed 

 near the vessels, whilst the true wood-fibres form most of the 

 harder summer-wood and are more numerous, the broader the 

 annual zone. 



3. Wood-cells forming parenchyma, or soft growing-tissue, are 

 more or less thinly walled and nearly isometric cells, usually 



with flat ends, and superposed one above the other like bricks ; 

 they contain starch, at least in the younger wood, for the greater 

 part of the year. They are thus the store-chambers for reserve 

 nutrient material, which may be used in ensuing years for 

 forming leaves, flowers and shoots. 



Wood-cells are chiefly found near the vessels, but often, as 

 for instance in oakwood, form concentric lighter-shaded zones 

 in the darker and harder summer-wood. 



In coniferous woods, wood-cells are either entirely wanting or 

 found only around the resin-ducts, or are scantily scattered 

 among the tracheids, as in juniper- wood. 



4. Resin-ducts are spaces without true walls, surrounded by 

 resin-forming cells ; they run not only parallel to the axis of the 

 tree, and are then visible on transverse sections, chiefly in the 



