Epigeal and hypogeal germination w/in a single species?

I am puzzled. Last yr. I collected a large number of spicebush (Lindera benzoin) seeds from shrubs in the area (I'm in northern VA, Appalachians). Some of them germinated w/out stratification and they all germinated epigeally, w/primary leaves appearing above the soil. Now, the second lot germinated in the spring after having been wintersowed outside all winter. A few are epigeal w/primary leaves above the soil, but most of these specimens have germinated hypogeally like peas w/the cotyledon below the soil and no primary leaves. How can there be hypo and epi germination w/in a species?

I have googled 'til the cows came home w/no luck.

Thanks for any input!

 

I've known acorns and hazel nuts to grow epigeally if they are on the surface and the shell is split, allowing the cotyledons to get sunlight. They turn green and open out flat, just like normal epigeal cotyledons of other plants. So clearly the distinction between epigeal and hypogeal is less absolute than one might think.

 

Fascinating! Acorns are usually thought of as being hypogeal germinators, correct? So, the pea-like cotyledons of the hypogeally germinating plant are the same structure as the primary leaf of the epigeally germinating plant...they just either stay closed (pea-like) or open as in the primary leaf? This would mean that almost any plant has the potential to become either hypogeal or epigeal?!

With the spicebushes, they were all sown in a similar manner (similar depth) so i'm wondering if the difference isn't in the stratification vs. non-stratification? Are there any other examples of plants that you can think of where stratification played a role in germination style?

Thanks!