20 PHARMACEUTICAL BOTANY 
that the cell walls of cellulose are stained a deep blue. A yellow 
line is evident in the middle of each cell wall and separates each 
cell from its bounding cells. This line represents the fused 
Fic. 11.—Elodea, an aquatic plant. 
primary walls of adjacent cells and is called the middle lamella. It 
is composed largely of calcium pectate. 
TypicAL GREEN CELLS 
Excellent material for the microscopic study of green cells of 
plants is to be found in the leaf of Elodea, a fresh water plant, 
found in ponds and house aquaria. The leaves of this plant are 
small enough to be mounted beneath an ordinary cover glass on 
a microscopic slide. They are oblong to oblong-ovate and 
occur in whorls of 2 to 4 along a slender, elongated stem. 
