GERMINATION 7 
Conditions 
In all cases, the conditions of germination 
necessary for are similar. The seed must have water; it 
Germination. 
must first be soaked and then kept coneney 
moist, for without water growth cannot take place. 
Secondly, it must have air. 
Thirdly, it must have food. 
This may be contained within 
the embryo, as in the cotyle- 
dons of the bean; or it may be 
external to the embryo, as in 
maize. 
Fourthly, a certain tempera-— 
ture is necessary. Seeds do not 
germinate when exposed to a 
— low temperature ; a cold spring 
keeps back the germination 
of the seeds planted in our 
gardens. 
Lastly, light, though not neces- 
sary for the first stages of ger- 
mination, is essential for the 
healthy development of the 
plant. | 
Mustard and cress, and seeds 
which have two cotyledons, 
develop as the sunflower or 
bean; seeds of grasses; and 
those- which have only one 
cotyledon, resemble maize in 
their development. 
Structure of Lue so-called 
Sunflower “seeds” of sun- 
— flower, those that 

Figs. 8 AND 9.—SEEDLINGS OF 
MaIzE. 
rt, primary root; rh, root- 
hairs ; dat, lateral roots; sec, 
secondary roots ; sh, root-sheath ; 
c, cotyledon ; », plumule. 
are bought from nurserymen, represent not only the seed, 
but also the seed-vessel. The brown, brittle shell is the 
wall of the seed-vessel, and answers to the pod of-the bean ; 
within this is a delicate whitish layer, the testa. 
