CHAPTER III 
MOVEMENTS, DEVELOPMENT, AND MORPHOLOGY OF 
THE SEEDLING 
28. How the Seedling emerges. As the student has 
already learned by his own observations, the seedling 
does not always push its way straight out of the ground. 
Corn, like all the other grains and grasses, it is true, sends 
a tightly rolled, pointed leaf vertically upward into the 
air. But the other seedlings examined usually will not 
be found to do anything of the sort. The squash seedling 
is a good one in which to study what may be called the 
arched hypocotyl type of germination. If the seed when 
planted is laid horizontally on one of its broad surfaces, it 
usually goes through some such changes of position as are 
shown in Fig. 9. 
The seed is gradually tilted until at the time of their 
emergence from the ground the cotyledons are almost 
vertical. The only part above the ground-line at this 
period is the arched hypocotyl. Once out of ground, the 
cotyledons soon rise until they are again vertical, but with 
the ends farthest from the hypocotyl at the top. Then 
the two cotyledons separate until they once more lie hori- 
zontal, pointing away from each other. Y 
‘Can you suggest any advantage which the plant derives 
from having the cotyledons dragged out of the ground 
rather than having them pushed out, tips first ? 
22 
