"P van Rijckevorsel" wrote in message
...

Are you sure you want to go there?
As I understand it the taxonomy of Betula is something else.
Just the difference between Betula pendula and Betula pubescens is enough
to
fill up any amount of time (provided you can read Russian; if not, you can
add a few years to learn that)
PvR

Let's hear it for the Atkinson Discriminant Function! :-)