Roscoea capitata
Encyclopedia
Roscoea capitata is a perennial herbaceous plant
native to the Himalayas, being found in Nepal
. Most members of the ginger family (Zingiberaceae
), to which it belongs, are tropical, but R. capitata, like other species of Roscoea
, grows in much colder mountainous regions.
native to the eastern Himalayas and in particular central Nepal
, where it is said to grow on grassy or stony hillsides and slopes, often on disturbed ground. The Flora of China also gives its distribution as "Xizang" (i.e. Tibet
), although this is not supported by other sources.
Like all members of the genus Roscoea, it dies back each year to a short vertical rhizome
, to which are attached the tuberous roots
. When growth begins again, "pseudostems" are produced: structures which resemble stems but are actually formed from the tightly wrapped bases (sheaths) of its leaves. R. capitata grows to 30–50 cm tall. The leaf blades are relatively long and narrow, 15–25 cm long by 1–3 cm wide, with a marked "keel" (i.e. they are folded along a central rib).
In its native habitats, R. capitata flowers between July and August. The flower spike has green bracts some 4–4.5 cm long by 1 cm wide which form a distinctive dense green "head", on a stem (peduncle
) 5–10 cm in length. Flowers then appear in succession from between the bracts. In the Flora of China, they are described as "blue"; elsewhere they are described as pink to purple.
Each flower has the typical structure for Roscoea
(see the diagrams in that article). There is a tube-shaped outer calyx, some 2.5 cm long, which is hairy (pubescent), particularly along the veins, and is split on one side with two teeth at the end. Next the three petal
s (the corolla) form a tube which is shorter than the calyx and terminates in three lobes, a more-or-less oblong upright central lobe, about 2 cm long, which is hooded, and two side lobes, longer than the central lobe. Inside the petals are structures formed from four sterile stamen
s (staminodes): two lateral staminodes form what appear to be petals, about 2 cm long; two central staminodes are fused to form a lip or labellum, about 2.5 cm by 1.4 cm, which is divided at the end into two lobes.
The single functional stamen has an anther about 5 mm long, with about 1 cm long spurs formed from the connective tissue between the two capsules of the anther. The ovary is pink and forms a capsule about 2.5 cm long after flowering when seeds are formed.
, who had previously created the genus Roscoea in 1806. It was described from specimens collected by the Danish botanist Nathaniel Wallich
. The specific epithet "capitata" has the meaning "forming a dense head", here referring to the way the flowers are borne.
In 1901, François Gagnepain
described two plants as varieties of this species: R. capitata var. purpurata and R. capitata var. scillifolia. Both are now considered to be separate species, R. cautleyoides
and R. scillifolia respectively.
.
Species of Roscoea divide into two clear groups, a Himalayan clade and a "Chinese" clade (which includes some species from outside China). The two clades correspond to a geographical separation, 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. capitata is part of the Himalayan clade, as would be expected from its distribution. It is most closely related to R. ganeshensis.
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
native to the Himalayas, being found in Nepal
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
. Most members of the ginger family (Zingiberaceae
Zingiberaceae
Zingiberaceae, or the Ginger family, is a family of flowering plants consisting of aromatic perennial herbs with creeping horizontal or tuberous rhizomes, comprising ca. 52 genera and more than 1300 species, distributed throughout tropical Africa, Asia, and the Americas.Many species are important...
), to which it belongs, are tropical, but R. capitata, like other species of Roscoea
Roscoea
Roscoea is a genus of perennial plants of the family Zingiberaceae . Most members of the family are tropical, whereas Roscoea species are native to mountainous regions of the Himalayas, China and its southern neighbours. Roscoea flowers superficially resemble orchids, although they are not related...
, grows in much colder mountainous regions.
Description
Roscoea capitata is a perennial herbaceous plantHerbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
native to the eastern Himalayas and in particular central Nepal
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
, where it is said to grow on grassy or stony hillsides and slopes, often on disturbed ground. The Flora of China also gives its distribution as "Xizang" (i.e. Tibet
Tibet
Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...
), although this is not supported by other sources.
Like all members of the genus Roscoea, it dies back each year to a short vertical rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
, to which are attached the tuberous roots
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...
. When growth begins again, "pseudostems" are produced: structures which resemble stems but are actually formed from the tightly wrapped bases (sheaths) of its leaves. R. capitata grows to 30–50 cm tall. The leaf blades are relatively long and narrow, 15–25 cm long by 1–3 cm wide, with a marked "keel" (i.e. they are folded along a central rib).
In its native habitats, R. capitata flowers between July and August. The flower spike has green bracts some 4–4.5 cm long by 1 cm wide which form a distinctive dense green "head", on a stem (peduncle
Peduncle (botany)
In botany, a peduncle is a stem supporting an inflorescence, or after fecundation, an infructescence.The peduncle is a stem, usually green and without leaves, though sometimes colored or supporting small leaves...
) 5–10 cm in length. Flowers then appear in succession from between the bracts. In the Flora of China, they are described as "blue"; elsewhere they are described as pink to purple.
Each flower has the typical structure for Roscoea
Roscoea
Roscoea is a genus of perennial plants of the family Zingiberaceae . Most members of the family are tropical, whereas Roscoea species are native to mountainous regions of the Himalayas, China and its southern neighbours. Roscoea flowers superficially resemble orchids, although they are not related...
(see the diagrams in that article). There is a tube-shaped outer calyx, some 2.5 cm long, which is hairy (pubescent), particularly along the veins, and is split on one side with two teeth at the end. Next the three petal
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...
s (the corolla) form a tube which is shorter than the calyx and terminates in three lobes, a more-or-less oblong upright central lobe, about 2 cm long, which is hooded, and two side lobes, longer than the central lobe. Inside the petals are structures formed from four sterile stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s (staminodes): two lateral staminodes form what appear to be petals, about 2 cm long; two central staminodes are fused to form a lip or labellum, about 2.5 cm by 1.4 cm, which is divided at the end into two lobes.
The single functional stamen has an anther about 5 mm long, with about 1 cm long spurs formed from the connective tissue between the two capsules of the anther. The ovary is pink and forms a capsule about 2.5 cm long after flowering when seeds are formed.
Taxonomy
Roscoea capitata was first described scientifically in 1822 by the English botanist James Edward SmithJames Edward Smith
Sir James Edward Smith was an English botanist and founder of the Linnean Society.Smith was born in Norwich in 1759, the son of a wealthy wool merchant. He displayed a precocious interest in the natural world...
, who had previously created the genus Roscoea in 1806. It was described from specimens collected by the Danish botanist Nathaniel Wallich
Nathaniel Wallich
Nathaniel Wallich was a surgeon and botanist of Danish origin who worked in India initially in the Danish settlement near Calcutta and later joined the East India Company...
. The specific epithet "capitata" has the meaning "forming a dense head", here referring to the way the flowers are borne.
In 1901, François Gagnepain
François Gagnepain
François Gagnepain was a French botanist. The standard botanical author abbreviation Gagnep. is applied to plants described by Gagnepain.-References:...
described two plants as varieties of this species: R. capitata var. purpurata and R. capitata var. scillifolia. Both are now considered to be separate species, R. cautleyoides
Roscoea cautleyoides
Roscoea cautleyoides is a perennial herbaceous plant occurring in the Sichuan and Yunnan provinces of China. The scientific name is also spelt Roscoea cautleoides . Most members of the ginger family , to which it belongs, are tropical, but R. cautleyoides, like other species of Roscoea, grows in...
and R. scillifolia respectively.
Evolution and phylogeny
The Zingiberaceae family 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 platesPlate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
.
Species of Roscoea divide into two clear groups, a Himalayan clade and a "Chinese" clade (which includes some species from outside China). The two clades correspond to a geographical separation, being divided by the Brahmaputra River
Brahmaputra River
The Brahmaputra , also called Tsangpo-Brahmaputra, is a trans-boundary river and one of the major rivers of Asia. It is the only Indian river that is attributed the masculine gender and thus referred to as a in Indo-Aryan languages and languages with Indo-Aryan influence...
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. capitata is part of the Himalayan clade, as would be expected from its distribution. It is most closely related to R. ganeshensis.