VI.] STONEWORTS. 49 



a. The terminal or apical cell: 



a. Its form: hemispherical, the rounded surface 

 free ; the flat surface attached to the cell below it. 



/3. Structure : sac, protoplasm, nucleus ; no vacuole 

 present. 



7. Sometimes two nuclei ; preliminary to division. 



8. Its mode of division; across the long axis of 

 the stem, giving rise to two superimposed 

 nucleated cells. 



b. The further fate of the new cells which are 

 successively segmented off from the terminal 

 cell; work back in your specimens from the 

 terminal cell. 



a. The new cells are successively nodal and inter- 

 nodal; the latter enlarge, develope a large 

 vacuole, and ultimately form the medullary 

 cells of the internodes; they never divide. 



^. The nodal cells divide freely, and do not 

 increase much in size ; they form the nodes, and 

 the cortical cells. 



c. The development of leaves: by the multiplication 

 and outgrowth of nodal cells. 



Their growth at the base, the terminal leaf-cell 

 soon attaining its full size and not dividing. 



d. The development of branches; from nodal cells 

 in leaf-axils, which take on the character of ter- 

 minal cells. 



d. The spore-fruits. 



Examine fresh, under a low power. 

 M. 4, 



