160 



PHYSIOLOGICAL BOTANY. 



c 



510, A, Lengthwise section of the Castor-oil plant. Beginning with the bark, r, cortical cells; gs, bun- 

 dle sheath; 5, bast fibers; p, bast parenchyma; c, cambium; the cells between c and p become sieve tubes; 

 *, t, pitted vessels ; q, shows an absorbed septum ; A", h", annular ducts; h, h, pitted vessels, resembling 

 annular ducts; 7, vessel apparently made up partly of annular cells and partly of reticulated cells; , spiral 

 vessel, of very small caliber, next to the pith; a', larger calibered spiral vessel; m, pith-cells. 



610, B y Lengthwise slice of wood from an Ailanthus glandulosa, highly magnified; g, g, pitted ducts; p,p, 

 wood parenchyma; If, woody fibers 5 st, st, cross-section of medullary rays; t, annular ducts. 



