TIJE STEM. 



tion ami enlargement of tlie cells throughout its whole length, 

 but as it gets older elongation for a considerable portion of the 

 internode ceases, and finally there comes a time when the culm 

 is incapable of furtlier elongation. If taken in hand when young, 

 and pro])erly shaded, a stem may be made to grow to an almost 

 indefinite lengtli. The lower portion of an internode of most 

 grasses, the part within the leuf-sheath, remains soft and continues 

 to grow for a considerable time after the upper and main portion 

 has lost this power. 



Fig. 5.— a cross-section of fibro-vascnlar bundle of Indian corn : a, side of bnndle 

 i?2£''^^ toward the circumference of the stem ; i, side of bundle toward the center of 

 stem , p, thm- walled cells of fundamental tissues of stem ; (/, (/, larse pitted vessels • s 

 l^r^I^L^IT^' *"' ""'' V-'^^ "^,*"' annular vessel . ?, air cavity funned bv the brealcing 

 J^K-} ^^, l^}? surrounding cells : f, r. latticed cells, or soft bast, a form ^f sieve tissue. 

 X 5a0.— (.A.fter Sachs ; notes after Bessey.) 



