Journal of Agricultural Research 
Vol. XXVII, No. 3 
158 
xylem. Both xylem and phloem are separated from the endodermis 
by a single-layered pericycle. 
The cortex forms a broad band of tissue composed of large cells with 
conspicuous intercellular spaces. The peripheral cells are covered by a 
root epidermis which soon becomes torn and is later replaced by a peri¬ 
derm. 
The secondary rootlets take their origin in the pericycle from meris- 
tematic cells opposite the protoxylem groups. There are commonly as 
many rows of lateral rootlets as there are protoxylem points. This corre¬ 
lation is well marked in certain overgrown roots, which show five or six 
prominent ridges and the same number of rows of lateral rootlets in the 
intervening grooves. 
EARLY DIFFERENTIATION AND DEVELOPMENT OF THE ROOT 
Even before the protoxylem points are differentiated sufficiently to 
effect union in the center, growth activity becomes evident in the central 
parenchyma. Due to this cell increase, the protoxylem groups are forced 
outward. Meanwhile, one of the most centrally located parenchyma 
cells has greatly enlarged and matured into a large xylem element. 
