There is pretty good precedent for griffons for Apollo.  Consider the pilaster capitals from the interior court of the Temple of Apollo: 4th c. BC, 1st, 2nd & 4th c. AD (under Caligula (37-41), Hadrian (117-138), and Julian the Apostate (361-363), never completed

Also, the temple of Apollo at Didyma has griffons on the frieze.

 And this from http://tinyurl.com/2njnab:

According to Walter Friedlander, in The Golden Wand of Medicine: A History of the Caduceus Symbol in Medicine, this connection can be traced back to 1902, when the U.S. Army adopted the caduceus as the insignia of its Medical Corps, which had previously used the cross. Earlier, in the 16th and 17th centuries, the caduceus had been used by printers because it was the staff of Hermes (Mercury) the messenger god, and hence the divine deliverer of information. In the 19th century, a medical publisher used the symbol prominently on its texts, and thereby began the association of the caduceus with medicine, an association made firm by the prevalence of the image in the American Medical Corps during World War I. A symbol first representative of wisdom, eloquence, and communication, thus became the common logo for those in the health profession.

Citing the history of the caduceus, some physicians are critical of the symbol, because Hermes also happens to be the god that leads the dead to the underworld and is not only associated with wealth and commerce, but happens to be the patron of thieves (he is a classic trickster figure in Greek myths). It only makes sense that doctors wouldn't want to be associated with trickery, death, and the accumulation of wealth! Medical purists suggest we should go back to the staff of Aesculapius, which is depicted as a single serpent coiled around a cypress branch.

The story of Aesculapius and his association with Hermes begins to make the story of the related symbols quite interesting. According to Greek myth, the god Apollo, in a fit of jealousy, killed his unfaithful mortal lover, a woman named Coronis (the Greek root of her name, korone, refers to a seabird, or a crow). When Apollo discovered that she was pregnant with his son, he had Hermes deliver the child while her body lay on the funeral pyre. The child was none other than Aesculapius.

Aesculapius was trained by the wise centaur, Chiron, to become a healer (since his father, Apollo, was the god of health), and over time, he became the god of medicine with his own cult and temples. Hippocrates, regarded as the father of western medicine, was a 20th-generation member of the cult of Aesculapius.

There are various explanations for why Aesculapius's symbol is the serpent coiled around a staff. The figurative interpretations consider the symbology (the snake's association with rebirth, the cypress branch as representing strength); and the utilitarian approach suggests that the snake was a poisonous one tied to the staff, its venom used for its medical properties. But the fact that Hermes was Aesculapius's deliverer does not quite explain how the messenger god ended up with the symbol for medicine or why the serpents were doubled (though the wings might be explained as a displacement of Hermes/Mercury's winged ankles).

There is also a significant history of corn and Apollo, but I can't find any specifics.  I'm sure other readers here have more useful info for you.  I am guessing, but I think the creator of the capitals in your picture was simply well-versed in classical ornament.  Good luck!

GFS