136 A TEXT-BOOK OF GRASSES 
GERMINATION 
170. The situation of the embryo in the grass seed is 
such that by the enlargement and growth of the organs 
the plumule and root at once emerge in opposite direc- 
tions. The seed remains in position, which is usually 
upon the surface of the ground. The primary root at 
first elongates but soon secondary roots appear which in 
a short time exceed the primary. The plumule pushes up 
somewhat later. The first leaf of the plumule acts as a 
protecting sheath and never develops into a foliage leaf. 
If the seed is below the surface of the soil this sheath, 
closed at the apex, elongates until the surface is reached, 
when the tip breaks and the bud pushes through. In 
many embryos there is a small scale-like organ (epiblast) 
at the base of the plumule opposite the scutellum. This 
is thought by some to represent a leaf, in which case the 
scutellum is the first leaf or cotyledon, and the pro- 
tecting sheath of the plumule is the third leaf. 
171. The germination of the maize is described at 
length by Collins. The protecting sheath he calls the 
coleoptyle. Between the coleoptyle and the seed is a more 
or less elongated axis to which the name mesocoty] is 
given. This portion is called by Hackel and others the 
epicotyl on the supposition that it is an internode above 
the cotyledon or scutellum. Collins and others consider 
the scutellum, epiblast and coleoptyle to be all parts of a 
highly specialized cotyledon. Collins also describes the 
germination of Hopi and Navajo varieties of maize in 
which the mesocotyl elongates greatly, reaching the 
enormous length of 25 or even 30 cm. The plumule is 
thus able to reach the surface from a corresponding depth. 
Such varieties are adapted to dry regions. The usual 
