LATICIFEROUS CELLS 121 



ring, and mount in water, or dilute glycerine : or stain 

 with alkannin, and mount in glycerine. 



Examine with a low power. 



Eunning through the cortical parenchyma will be 

 seen long tubes, with thick cellulose walls and granular 

 contents. These are the laticiferous cells, which 

 differ from the preceding in being developed, not by 

 fusion of originally distinct cells, but by continued 

 apical growth of single cells. 



Note cases of branching of these cells. 



Included in the granular contents are starch-grains 

 of peculiar dumb-bell form. 



Treat sections with iodine solution, and observe the 

 effect on these bodies. 



II. Cut transverse sections of the same stem, and 

 note the distribution of the laticiferous cells ; they may 

 be recognized by their walls, which are thicker than 

 those of the surrounding tissues, and appear circular in 

 section. 



III. Separate the whole cortex from a piece of the 

 stem ; boil it in potash for about five minutes, and 

 tease out the long laticiferous cells with needles ; mount, 

 and observe with a low power. They appear as long 

 cylindrical tubes, with thick walls. Observe occasional 

 branching. They are usually broken at the ends, the 

 length of the tubes being greater than that of the 

 parts teased out. 



In longitudinal sections through the apical region of the stem 

 of Euphorbia it may be shown by staining with haematoxylin 

 that numerous nuclei are present near to the blind endings of the 

 tubes. 



