42 



CORN 



1. Young root ot a pea. h Root-hairs of the piliferous layer; c root-cap. 

 (Twice natural size.) 



2. Transverse section through a young root of a pea near h in 1. h Root- 

 hairs; c cortex; p piliferous layer; e endiodermis; n pericycle; w wood 

 strand; x its protoxylem; b bast strand. (Enlarged 4S diameters.) 



STALK. — Structure of Stem. The stem varies in height from i8 

 inches to 24 feet, according to variety and conditions influencing 

 growth, as climate and soil. It is made up of a series of sections 

 known as intcnwdcs, which vary in length from a few inches at the 

 base to more than a foot at the top. They are separated from each 

 other by short, thick joints or nodes. Tlie length of internodcs is less 

 at the base for the purpose of strengthening the stalk. Being longer 

 at the upper end, the stalk has more chance to flex in the breeze with- 

 out breaking. The average circumference of the nodes measured on 

 ten stalks was about as follows : Second internode above root crown, 

 3.7 inches; first internode below the ear, 3.3 inches; first internode 

 above the ear, 2.875 inches. 



The stem of the corn plant consists structurally of 



(i) .A. very thin layer, the epidermis, on the outside. This con- 

 sists of a one layered cylinder of cells. The surface is very smoolll 

 and glossy, being impervious to moisture. The idea that a corn stalk 

 "drinks in" the showers is erroneous, as shown by this impenetrable 

 coat. ( )n the oth<^r hand, this covering lessens the evaporation of 



