Several conundrums also inhabit the common name: Marsh Grass-of-Parnassus. Although it starts out well – this circumboreal species grows in cool, wet soils and the species name palustris is Latin for boggy or marshy – the Grass and Parnassus are not immediately self-explanatory. Mt Parnassus is a hunk of limestone that rises to 2,457 m (8,062 ft) between the 38th and 39th parallel in Greece, a land not known for an arctic climate nor an abundance of water. Linnaeus named Parnassia for the mountain, and the plant is supposed to like calcareous soils, but the slopes are unlikely to have been covered with Grass-of-Parnassus. Perhaps, at least in antiquity, Mt Parnassus had lots of boggy meadows and springs. And in antiquity, I think, lies the grass conundrum. Although a modern grass should reside in the Graminaceae (or if you prefer, Poaceae) along with corn, wheat, rice, barley, oats, and a weed-free lawn, according to the OED the basic meaning is nowhere near so phylogenetically precise. The first definition of ‘grass’ is of low herbage eaten by livestock and ‘Gramineae' doesn’t rate a mention until definition 4b (ahead of the fumitory usage at 7).
Continuing with the antiquity theme, Mt Parnassus was reputed to be the home of the Muses: the water nymphs credited with inspiring poetry, literature, and learning. They were protected by Apollo and associated with the springs of Helicon and Pieris (perhaps good places for Grass-of-Parnassus to grow). This is entomologically interesting because Heliconius (as opposed to Heliconia, a genus of plants) and Pieris are genera of butterflies (the former including many colourful but mostly tropical butterflies, and the latter the Cabbage White). Parnassius is also a genus of butterflies that includes the Mountain Apollo, P. apollo. Butterflies, however, do not seem to be attracted to Grass-of-Parnassus, which is reputed to be pollinated primarily by flies. And there’s another fly in the ointment: conflicting information about pollination in Parnassia. Some sources claim the plant fools its flies with fake rewards and some that it provides nectar. Some claim that it is outcrossing, others that the anthers dump pollen directly on the stigma. Based on a study by Sandvik and Totland (2003, Can. J. Bot. 81: 49–56) of two populations of P. palustris in Norway, these conflicting claims all have some merit.
Parnassia flowers are 2-3 cm in diamter and its floral parts are in whorls of 5: calyces, petals, and anthers. It is protandrous, i.e. male first – the anthers usually mature and release their pollen before the ovary is receptive. This promotes outcrossing and Sandvik and Totland found outcrossing dominant in one of their populations, but not in the other. Flies were the primary pollinators, although the species differed between populations, and these results are consistent with other studies. Hoverfies (Syrphidae, e.g. Sphaerophoria, Eristalis) are of especial importance, but members of the Tephritidae, Muscidae, Dolichopodidae, Anthomyiidae, Phoridae, and Empididae also have a role to play in various parts of the World.
As well as the usual fertile anthers that produce the pollen, however, Parnassia also has sterile anthers, called staminodes, that are divided into thin rays with shiny, rounded knobs at the tips that resemble nectaries, but do not produce nectar. These false nectaries do fool inexperienced flies, but two real nectaries are present below each cluster of rays that produce both nectar and a honey-like scent. When staminodes were experimentally removed from flowers, Sandvik and Totland found that flower visitation rates were less than half of that in intact flowers, flies spent little time in flowers without nectaries, and seed set was poor. So, rather than cheating its pollinators, the staminodes simply mislead them, a harmless bit of hyperbole that makes the flowers seem more attractive from a distance (although one supposes that there may be flies that never figure it out).