In message , Nightingale
writes
I have a couple of questions I was hoping someone could help with....

Given the following two names:

Tillandsia usneoides fo. longissima André, 1889
Tillandsia usneoides var. longissima (André) Mez, 1896

What is the difference between the two? I assume var. stands for
variety, but what does fo. stand for? Form? Is this a case where the
same plant was reclassified a few years after discovery, or are they
two separate plants?

Thank you for your help,

-N
They're almost certainly the same plant. The presence of the name André
in the second name means that it's plant originally named by André but
reclassified in a different higher taxon, or in this case, at a
different rank.

I don't recall seeing fo. as an abbreviation before (f. is more usual),
but I assume that it represents form/a.

The other possibility is that André described Tillandsia usneoides fo.
longissima and Tillandsia otherspecies infra longissima (infra standing
for any infraspecific rank), and Mez transferred the latter into
usneoides. I don't understand the minutiae of the ICBN sufficiently, but
I suspect that would have been an error.

To complicate the issue, IPNI has it as T. u. var. longissima André.
--
Stewart Robert Hinsley