HOW CHARACTERS ARE TRANSMITTED 125 
bearing both silk and tassel and producing both ovules and pol- 
len grains, each new kernel being independent of its neighbors. 
Fertilization in general. 
This, roughly speaking, is 
characteristic of fertilization 
in general, whether plant or 
animal. A small male cell 
(the pollen grain in plants or 
the spermatozodn in animals) 
meets and fuses with the 
larger! female cell (ovule in 
plants or ovum in animals), 
which is thereafter capable 
of developing into a new in- 
dividual possessed of all the 
characters of both parents. 
The method of effecting 
this union of the nuclei in 
fertilization and the time at 
which it takes place vary 
greatly in different species. 
In many plants both sex cells 
are borne by the same indi- Fic.19. Kernels of corn growing on 
vidual, ater Mone flower, the tip of i ae ee aaa but 
as in the apple and the elm, 
or in separate flowers, as in corn? In others, as the chestnut and 
the box elder, the male flowers are borne on one plant and the 
1 Though the female cell is always larger than the male, the nucleus, which 
seems to be the essential part, has the same number of chromosomes (see 
chromosomes), so that the male and the female parents have identical powers 
in transmission. The differences in size are apparently due to the amount of 
protoplasm surrounding the nucleus, probably as food material for the develop- 
ing young and in no way connected with heredity. This difference is some- 
times great, as in the egg of the hen, most of which is food material for the 
developing chick, while the male cell is microscopic. 
2 This bisexuality, or hermaphroditism, is also found in certain lower animals, 
as the earthworm. 
