GERMINATION AND GROWTH 45 
“ peg ”’; can you tell its use? Could the cotyledons get out 
of their hard covering without it? Slip the peg below the 
coat in one of your growing specimens, leave it in the soil, 
and see what will happen. How do the cotyledons of the 
squash differ from those of the bean as they come out of the 
seed cover? Do they act as foliage leaves? Do you see 
any difference in the development of the plumule in the two 
seeds (Figs. 19, 25) to account for the different behavior of 
the cotyledons? Sketch three seedlings in different stages, 
labeling correctly the parts observed. Make a similar study 
of the castor bean, or other seedling selected by your teacher, 
and illustrate by drawings. 
44. Arched and straight hypocotyls. — This difference in 
the manner of getting above ground is an important one. 
That by means of the arched hypocoty] is, in general, charac- 
teristic of the process of germination in which the cotyledons 
come above ground, while the straight kind, which was illus- 
trated in the corn and wheat, is the prevail- 
ing method when the cotyledons remain 
below ground. Can you give a reason for 
the difference? 
45. Polycotyledons; germination of the 
pine. — Examine a pine seedling just begin- 
ning to sprout. What part emerges first 
from the seed coat? Where does it break 
through? Where did you find the micropyle 
in the pine seed? (15.) Can you give a 
reason why the hypocotyl in seeds should 
break through the coats at this pomt? How frie. 60. — Pine 
do the cotyledons get out of the testa? Is seedlins(4/terGray). 
the hypocotyl arched or straight in germination? How does 
it compare with the bean and squash in this respect? With 
the corn? Is any endosperm left in the testa after the cotyle- 
dons have come out? What has become of it? Do the 
cotyledons function as leaves? How many of them has the 
specimen you are studying? Notice the little knob or button 
