THE STEM. 7 



tion and enlargement of the 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 further elongation. If taken in hand when young, 

 and properly shaded, a stem may be made to grow to an almost 

 indefinite length. The lower portion of an internode of most 

 grasses, the part within the leaf -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- vascular bundle of Indian corn : o, side of bnndle 

 looking toward the circumference of the stem ; i, side of bundle toward the center of 

 stem ; p, thin- walled cells of fundamental tissues of stem ; {/, a, large pitted vessels ; 8, 

 spiral Vessel; r, one ring of an annular vessel : ?, air cavity formed by the breaking 

 apart of the surrounding cells : c, r, latticed cells, or soft bast, a form of sieve tissue, 

 x 550. (After Sachs ; notes after Bessey.) 



