"Exotica" is listed in the Guild Handbook on page 551, bibliography
for "Illustrating Plants" chapter under Graf, A.B. 1982.  "Pictorial
Cyclopedia of Exotic Plants."  Exotica Series 4, International.  East
Rutherford, NJ:  Roehrs.  Another related book listed under same
author, 1978, is "Tropica," same publisher Roehrs.  Probably newer
editions are out.  I have found "Exotica" useful on several
occasions.  The photos are pretty good.  I don't remember if my
husband has the "Tropica"  volume.

By the way, in answer to the question about the Medical Models Board,
possibly called dull-finish stipple board, the Medical Models
Laboratory phone number is 410-358-9199, page 536 of the Handbook
(where the area code is wrong - Baltimore and eastern Maryland now
are 410 instead of 301).  On the instigation of Leon Schlossberg,
medical illustrator at Johns Hopkins Medical School, this board was
developed when Ross board disappeared.  Mrs. Baldwin at Medical
Models Lab tells me that the board is not available right now but
probably will be in a few months.  If you send her your address, she
will notify you of its availability.

Isn't everything in the Guild Handbook?

Elaine