I never thought of germinating in them.
By the way, humidity and oxygen DO diffuse slowly through the plastic and through the "zipper".
I have just a few large glassine envelopes, but those are great for bundling together several 2x3" plastic Ziplocks without taking up more space.
I've read that, if you have dust-like seeds trying to jump out of a plastic Ziplock due to static electricity, you can calm them down by wiping the OUTSIDE of the Ziplock with a clothes-dryer anti-static sheet.
And I've tried that. Usually the seeds just fall right down and behave, but not always.
