CELL-NUCLEUS—FERTILISATION 247 
of the ovule the embryo begins to develop. 
Gradually the ovule changes into the seed. 
Reserve materials of food accumulate within 
it, and are most frequently stored either 
in the growing endosperm, or partly (seldom 
wholly) in the sporangium wall (nucellus, 
perisperm). If the embryo reaches any con- 
siderable size within the seed, it may presently 
destroy these tissues, and absorb the nutritive 
contents into its own body. When this 
happens, some part of the young plantlet 
usually becomes thickened and so forms the 
repository for the food. Most commonly it 
is the seed leaves (cotyledons), as in the 
bean, or it may be the young stem below 
them, as in the brazil-nut, which thus becomes 
charged with the reserves of food. 
In whatever way the food material is dis- 
posed, however, it is always so situated as to 
be readily available when the young plantlet 
starts into growth, on the germination of the 
seed. 
It does not invariably happen that con- 
siderable stores of food after this fashion 
await the embryo on its awakening to its 
new life. Many of the flowering plants have 
followed other lines than that of transmitting 
to a relatively small posterity large accumula- 
tions of hereditary capital. The commonest 
alternative is seen in the production of vast 
quantities of small seeds. The seed and the 
contained embryo have been well cared for 
during the earlier stages—but they are cast 
