Roscoea scillifolia
Roscoea scillifolia is a perennial herbaceous plant occurring in Yunnan in China. Most members of the ginger family, to which it belongs, are tropical, but like other species of Roscoea, R. scillifolia grows in much colder mountainous regions., the species is only known in cultivation and may be extinct in the wild.
Description
Roscoea scillifolia is a perennial herbaceous plant. Like all members of the genus Roscoea, it grows from a short rhizome, to which the tuberous roots are attached. When growth begins again, "pseudostems" are produced: structures which resemble stems but are actually formed from the tightly wrapped bases of its leaves. R. scillifolia varies considerably in height, extreme forms being as short at 6 cm, with some plants up to 37 cm tall; most are between 10 and 27 cm. There are up to three bladeless sheathing leaves and one to five full leaves, again varying considerably in size. The blade of the leaf is typically 11–22 cm long by 1.5–2 cm wide. At the junction of the blade and sheath there are small transparent structures, 2–3 mm high.The stem of the flower spike may or may not emerge from the leaf sheaths. A single flower is open at any one time. The flowers may be pale in colour or dark purple. Green bracts, 2.6–5 cm long subtend the flowers.
Each flower has the typical structure for Roscoea. There is a tube-shaped outer calyx, about 1.5–2.3 cm long. Next the three petals form a tube about 1.6–3 cm long, almost entirely hidden within the calyx. The tube terminates in three petal lobes: an upright central lobe and two slightly shorter side lobes. The central lobe is about 1.4–2 cm long by 0.6–1 cm wide; the side lobes are somewhat smaller, 1.1–2 cm long by 0.4–0.7 cm wide. Inside the petals are structures formed from four sterile stamens. Two lateral staminodes form what appear to be small petals, about 1–1.4 cm long by 0.3–0.5 cm wide, including a short narrowed "claw" at the base. Two central staminodes are fused at the base to form a lip or labellum, about 1.3–2 cm long by 0.8–2 cm wide. The labellum varies in how far it is split at the end into two lobes. It typically has white lines at the base.
The single functional stamen has a white anther, about 5 mm long, and the typical Roscoea "spurs" on the filament. The triangular ovary is 1–1.5 cm long.
There are two named forms of the species. The nominate form, R. scillifolia f. scillifolia has pale flowers, usually pink or white. R. scillifolia f. atropurpurea has dark purple flowers, and a significantly longer floral tube and surrounding bract.
Taxonomy
R. scillifolia was first described by François Gagnepain in a 1902 publication as R. capitata var. scillifolia. The description was based on specimens collected in 1887 and 1888 by Père Jean Marie Delavay from Heechanmen, near Dali in Yunnan. The variety was raised to a full species by Jill Cowley in 1982.For a long time the species was incorrectly known in horticulture as R. alpina. Cowley cites articles written in 1938, the 1960s and 1970, all of which use this name for what is actually R. scillifolia.
Evolution and phylogeny
The family Zingiberaceae is mainly tropical in distribution. The unusual mountainous distribution of Roscoea may have evolved relatively recently and be a response to the uplift taking place in the region in the last 50 million years or so due to the collision of the Indian and Asian tectonic plates.Species of Roscoea divide into two clear groups, a Himalayan clade and a "Chinese" clade. The two clades correspond to a geographical separation, their main distributions being divided by the Brahmaputra River as it flows south at the end of the Himalayan mountain chain. It has been suggested that the genus may have originated in this area and then spread westwards along the Himalayas and eastwards into the mountains of China and its southern neighbours. R. scillifolia falls into the Chinese clade as would be expected from its distribution.