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 

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

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

 the dermatogen at the 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) ; *, r. the cor- 

 tex which is produced from the periblem at the apex ; m, g.f, the plerome; m be- 

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

 inner and younger portion of the root-cap. After Sachs. 



