The message
from "Franz Heymann" contains these words:

So does mine, and so does The Plantfinder.
Sacha, how many have you sold with a wrong spelling for the name?
{:-))

Well you all had me looking it up as well because I have always spelt
it Schizandra ...

Seems either is/was correct. L. H. Bailey - published 1947 - has it with a Z,
Sanders - the 1950's edition - has Schisandra but notes it can be spelt
Schizandra.

Jennifer