If its from Tenerrife, then its highly likely to be a 'dragon tree' (Dracaena draco) Its like a national emblem for the island and a big tourist attraction, they recon some of the trees are 2 thousand years old or more!
Its not very thoughtful of them, not to indicate which end is the bottom etc, if you planted it up the wrong way it would'nt stand a chance. I have a differant type of dracaena and I've just checked the leaf-scars and they have a concave shape (dished) to them, hope that helps.
I grew one once from some seed that someone brought me back as a souveneer and kept it growing for a few years.
The tree does look similar to a yucca when small and has a red sap known as dragons blood, lots of folk-lore attached to it.
I've never tried growing a log but wish you sucsess.
Ps One solution may be, saw it in half and plant one up one way and the other, the other way, at least you will have a 50-50 chance. Good Luck.