This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
There are not any instances of the occurrence of Grass of Parnassus in early beds. It is confined to the North Temperate Zone of Europe, N. Africa, Siberia, Western Asia, as far east as N.W. Himalayas, E. and W. North America. It is found generally in Great Britain, but not in the Peninsula province in Dorset; and in S. Hants only in the Channel province; not in Kent or S. Essex in the Thames province; throughout Anglia; not in W. Gloucs, Monmouth, Hereford in the Severn province. In Wales it occurs only in Carnarvon, Denbigh, Flint, and Anglesea; in the Trent province; throughout the Mersey, Humber, and Tyne provinces; and in the Lakes province generally, except in the Isle of Man. It is found in the whole of the W. Lowlands; not in Peebles or Selkirk in the E. Lowlands; or Stirling, N. Perth in E. Highlands; throughout the W. Highlands, except in N. Ebudes; and in the N. Highlands, except in W. Ross; in the North Isles, except in the Hebrides. It is found at 2700 ft. in the Highlands.
This beautiful plant is one of the features of bogs in the autumn, when its white flowers are scattered in profusion over the flat water-meadows around more truly boggy tracts. It is found in such places as the Great Spearwort, Sundew, Bog Pimpernel, Water Violet, Bog Speedwell, Marsh Lousewort, Butterwort, Bladderwort, Bog Bean, Marsh Helleborine, Marsh Orchis, Cotton Grass, and other hygro-philous or helophilous plants frequent.
This is not a grass, but a delicate herbaceous plant, with few flowering stems, slender, erect or wavy, angular, bearing a single, clasping, stalkless leaf halfway up the stem. The radical leaves are stalked with a heart-shaped form. The plant has the rosette habit.
The flowers are of a beautiful cream or white colour, with free, blunt sepals. The veined petals have a short claw, and the honey is contained in fringed petal-like yellow scales or nectaries. There are 4 stigmas. The flower in sunshine is sweet-scented, but loses its scent at night. The Grass of Parnassus is about 10 in. high at its best. It is a late-flowering plant, blooming from August to October. The plant is a deciduous, herbaceous perennial, increased by division.
Only 5 anthers are borne on the 10 stamens, the others are melliferous at the bottom, and are crowned by as many as 17 yellow globular glands, resembling honey, but dry. They may serve to attract flies. The immature anthers lie near the conical ovary, which rises up in the centre and overtops them. They ripen first successively, and elongating come to just above the top of the stigma, with the back to it, and open away from it, and as each does this another follows each day, and afterwards the stigmas on the sixth day develop. The nectaries are just opposite each petal, alternate with the stamens, and each is shortly stalked, with a broad, fleshy disk, secreting honey in two hollow depressions, or on the inner side, and they leave it fully exposed. The yellow-knobbed glandular bodies or staminodes surround the base of the ovary, and render the nectaries conspicuous, but they are dry though they look like drops of liquid, and flies are deceived by it, the smaller travelling round the flower, the larger resting in the middle, dusting their sides with pollen in younger flowers, cross-pollinating older ones if they pass out to them. The visitors are Eristalis, Helophilus, Syrphus, Melanostoma, Melithreptus, Syritta, Sarcophaga Pollenia, Tipula, Tenthredo, Ichneumonids, Pem-philus, Gorytes, Coccinella.
The capsule is many-seeded, and is membranous, allowing the seeds to be emptied out by the wind. The seeds are minute and weigh only .00003 of a grain.
Photo. Flatters & Garnett - Grass of Parnassus (Parnassia palustris, L.) (probably var. condensata, Wheldon and Travis)
A cluster-cup fungus, Uromyces parnassioe, attacks the Grass of Parnassus.
Parnassia, Linnaeus, is from the Mount of Parnassus, and was called gramen parnassium by Dodonaeus. The second name (also Latin) refers to its paludal habitat.
Grass of Parnassus is called White Buttercups, White Liverwort.
Essential Specific Characters: III. Parnassia palustris, L. - Stem erect, short, radical leaves petio-late, cordate flowers solitary, white, large, petals veined, with claw, with scales or nectaries fringed with hairs, and yellow glands.