Well, just like in a lily seed pod, usually the "top" ones towards the opening in the pod are bigger and better seeds.
But you can just emptu the pod on a newspaper and by comparison, choose the big ones.
You should feel/see there is something inside not just a see-through thing.
I never sowed any gladiolus seeds cause there's so many small corms in the ground surrounding the big one.
And also, I am not sure this Gladiolus comes true from seeds... there may have been so much hybdridizing going on... unless you have some species gladiolus (like, wild type)
