160 



BOTANY. 



ing less perfectly developed tissues and tissue systems. Their 

 epidermal system is more feebly developed, and they bear very 



Fig. 137.— Longitudinal section through the apex of a root of Indian corn {Zea 

 inftaiH). All within and above the line t), s, v, is the loot proper,, all below and outside 

 of it is the root-cap, or inleorhiza; a, apex of root ; e, e, epidermis, continued into 

 the dermatogen at tne apex ; v.v^ the thickened outer wall of the epidermis (the 

 origin of the root-cap from the dermatogen is not shown in this figure) ; cd, ?■, the cor- 

 tex which, ie produced from the periblem at tte apex \ m, g^f, t)ie plerome ; m be- 

 comes the pith, g a vessel, /, wood ; a, a, outer and older portion of the root-cap ; £, 

 Inner and younger portion of the root-cap. —A iter Sachs. 



