THE STEM AND ITS FUNCTIONS 



97 



Bast. — The fibro-vascvilar e3'liii(ler is composed of two tlistinct 

 tissues. On the outside is the bast or phloem, the function of 

 which is to transport the elaborated foods — the carbohydrates, 



--Bast Fibers 

 ^7-- Sieve Tube 



Cambium 



Wood Ray 



- Wood Fibe- 



Fig. 49. — Transvert^e .seciion of wood and bast of the tulip-tree (Liriodendron) . 

 A portion of Fig. 48 more highly magnified, including part of one of the segments 

 between two wood-rays. The last annual ring of wood, together with one of the 

 groups of bast cells, is included. 



fats, and proteins — from one part of the plant to another, 

 especially from regions of manufacture to those of storage or 

 consumption. The cells concerned in this process are the sieve- 

 tubes (Fig. 51), living cells with thin cellulose walls but unique 



