The Story -Book of the Fields 



of them is formed every year. During the 

 warm weather a special fluid is produced by 

 the whole tree ; this is the sap, the liquid 

 food of the plant. This liquid passes 

 between the wood and the bark, and in its 

 course gradually becomes on one side a layer 

 of wood moulded on the exterior of that of 

 the preceding year, and on the other a thin 

 sheet of bark, in addition to that which is 

 already formed. 



Thus in every year, for the bark as well as 

 the wood, a fresh growth takes place. But 

 the added growth is deposited on the two 

 sides in an opposite direction ; on the out- 

 side for the wood, on the inside for the bark. 

 The wood, clothed in successive years by a 

 new ligneous layer, grows old at the centre 

 and young again on the surface ; the bark, 

 being lined each year by a fresh sheet, grows 

 old on the outside and young on the inside. 

 The former buries its worn-out and dead 

 layers in the interior of the trunk, the latter 

 casts outside its old growths, which crack 

 and fall away in rough scales. The wearing- 

 out proceeds simultaneously on the surface 

 and at the centre of the tree, but, at the 

 limit of the wood and the bark, life is always 

 at work with new growths. 



I* 



