THE CELL AND TISSUE. 73 



contained in special elongated cells called the laticiferous ves- 

 sels. Cork tissue is composed of cells whose walls are thin 

 and impermeable to liquids and gases. 



14. The gro"wing point of stems and roots is composed of 

 delicate cells, thin-walled and rich in protoplasm. By their 

 multiplication the stems and roots are lengthened. The scales 

 (leaves) of the bud cover the growing point of the stem (Fig. 

 112). A root-cap protects the growing point of the root (Fig. 

 113). The outermost cells are abraded as the root-tip pene- 

 trates the soil, but the cap is constantly renewed by the mul- 

 tiplying cells of the growing point. 



G 



