Hi Zach,
I'm not a biologist so I hope I'm not disqualitfied... Anyway,
Yes, seed does have to be wet in order for stratification to work.
I suppose some species have different approaches to it but the most
often used way is a hormone that breaks down over time only below
a certain temperture. Plants from areas closer to the poles (mostly
northern plants) will give their seed more of these hormones so
that they remain dormant for longer. If the seed starts germinating
early during a warm spell only to refreeze, it's death for them.
Of course, the seeds will not be given equal amounts so some will
still start early and others may wait for a whole extra year.
> And finally, I've heard the seeds must
> be exposed to at least frost to germinate.
These is not stratification but scarification. This means that
the seed coat needs to be damaged so the seed can imbibe. Usually
such seed doesn't need stratification on top of the scarification.
Often, some animal's digestive tract supply the right treatment.
To get such seeds germinated, people can soak them in sulfuric
acid for certain lengths of time. No CP need this treatment!
No scratching the seed coat, ect. The smoke treatment is not
scarification either, but is more similar to stratification. It
lets the seed "know" when to come up and is not a method to
survive their scattering via animals.
Dave Evans