SEEDLINGS OF THE GRASS TYPE 105 
in connection with it, there is a principle which is reckoned 
with in growing certain plants of the Grass type. According 
to the depth of planting this temporary stem region is long or 
short. (Fig. 97.) This is due to the fact that the first node and, 
consequently, the first of the permanent roots are always estab- 
lished about the same distance under the surface of the soil, re- 
gardless of the depth at which the seed was planted. Therefore, 
eZ, 
rst 
Gx: | 
A-} 
ae em Bb 
Se 
B 
Fic. 99.— Stages in the development of the Onion seedling. A, section 
through an Onion seed showing endosperm (en) and embryo (e) with the 
hypocotyl (h) and cotyledon (c) indicated. B, seed germinating; g, ground 
line; s, seed; c, cotyledon; h, hypocotyl; r, radicle. C, seedling more de- 
veloped; c, cotyledon which is being pulled out of the seed; h, hypocotyl; 
r, radicle; f, first leaf. D, a later stage of the seedling with cotyledon free 
from the seed and permanent root system (p) developing. 
a deep permanent root system, which is often desirable in order 
that the plant may withstand drought, is not secured by deep 
planting — a fact which has been well demonstrated in case of 
Corn and the small grains. Moreover, if the seed is planted too 
deeply, its food and energy may be exhausted before the plumule 
reaches the light, in which case the seedling is unable to continue 
its development. 
However, after the permanent roots are established they may 
