i8o 



Elementary Biology. 



larly known as annual rings. These rings are not so distinct 

 in the bast, for there is not so much of it formed, nor is it 

 formed so regularly. This formation of new layers of wood 

 and bast may go on for an indefinite number of years, hence 



FIG. 94. DEVELOPMENT OF THE DICOTYLEDONOUS STEM. (Sachs.) 



K, cortex : M, pith ; zV, interfascicular cambium ; fc, fascicular cimbium ; 

 /, primary phloem ; .r, primary xylem ; l>, hard bast ; f/i, ifh. fascicular 

 and interfascicular wood. 



the term open, or capable of continuous growth, as applied 

 to strands of the dicotyledonous stem. Manifestly as the 

 stem thus increases in size, some arrangement must be made 

 whereby the cortex may increase concomitantly. Such an 



