φημι... has enclitic forms in the present active indicative (except 2nd sing. φης).
But on page 271, in the excerpt from Plato (Gorgias 456a-c), a sentence begins:
fhmi\ de\ kai\ ei)s po/lin...
Why is φημι accented on the ultima? Is it because it's at the beginning of the sentence? Mastronarde mentioned this behavior with ειμι (be) but never with φημι as I recall.
