DEVELOPMENT OF THE SEED 287 
lying one of these develops, the others perishing. So the 
ovule comes to have one megaspore, which is retained in 
the ovule tissues. A little later this megaspore develops 
an egg in connection with a greatly reduced archegone, 
and a very immature gametophyte, in the following 
manner: 
The nucleus of the megaspore divides into two, which 
move to opposite poles of the megaspore cavity; here 
they divide twice resulting in four nuclei at each pole; 
then a nucleus from each pole (the so-called polar nuclei) 
moves to the center, where they ultimately unite. At 
the upper (micropylar) end one of the (naked) cells 
becomes the egg, accompanied by two companion cells 
Fie. 160.—Ra- Fie. 161.—Ranunculus (de- Fic. 162.—Pol- 
nunculus (pistil velopment of ovule). len,tubular anthe- 
and seed). rid and sperms. 
(““synergids’’). At the lower end are the antipodal 
nuclei (or cells). About this time any pollen cell (micro- 
spore) that may have fallen upon the soft tissue of the 
carpel stigma germinates there producing its most 
reduced gametophyte, and a tubular antherid (pollen 
tube). The latter penetrates the soft stigma tissues 
toward the ovary cavity, carrying down the two sperms. 
When the tubular antherid reaches the ovule it enters 
_ the little pore (micropyle) at the summit of the indusial 
coats, and penetrates the ovule to the egg where one of 
the sperms then unites with the egg, this constituting 
fertilization. The zygote now divides repeatedly and 
