THE STEM AND ITS FUNCTIONS 



99 



Fig. 51 —The strut-ture of a sieve-tube (Squash). .1, longitudinal section of 

 a sieve-tube, communicating bj- sieve-plates with the adjacent sieve-tubes above 

 and below. Its companion-cell is at the left. B, transverse sections through 

 two sieve-tubes. The one at the left is cut near the middle. The one at the 

 right IS cut near the end, its end wall, or sieve-plate, showing in the section 



