Apostrophe question

[David Smith <david.smith@gmail.com>]

I've read a number of Ada tutorials now, and I'm unclear on when the
apostrophe is required in certain spots.  For example, why is it used
here:

Father : Person_Access := new Person'(Father_First_Name,
Father_Last_Name);

but not here:

type Float_Array is array(Integer range <>) of Float;
type Float_Array_Access is access Float_Array;
V : Float_Array_Access := new Float_Array(1 .. 3);

I'm sure there is a page about this somewhere, but I can't find it.
If someone could point me in the right direction, I'd appreciate it.

-Dave