Cautleya

''Cautleya'' is a small genus of perennial plants of the family Zingiberaceae (the ginger family), found in the eastern Himalayas through to China and Vietnam. It consists of two species of high-altitude tropical and temperate plants, native to cool forest areas – an unusual habitat for members of the Zingiberaceae. They are grown as ornamental flowering plants.

Description

''Cautleya'' species grow from short rhizomes which have thick, fleshy roots. They have "pseudostems" formed by the tightly wrapped basal sheaths of their leaves. Depending on the species, the pseudostems may be high. Individual leaves consist of a sheath and a blade. At the junction of the sheath and blade, there is a stalk ( petiole), which may be very short or absent. The plants die back in the winter with shoots appearing again in spring.

The yellow or orange flowers appear in the summer and are grouped into a spike (inflorescence). Each flower is surrounded by a persistent coloured bract. The sepals are joined to form a tubular calyx, divided on one side. The bases of the petals are fused to form a tube as long as or longer than the calyx. At the end of this tube the three petals form separate lobes: the central lobe is upright and narrower than the two side lobes. Inside the petal tube there are three petal-like structures (formed from staminodes). The side staminodes are upright. The broad central lip or labellum is bent downwards. It has a narrowed section (claw) at its base which is joined to the side lobes of the petal tube.

There is a single stamen with a short upright filament. Connective tissue at the base of the anther forms a fork-like appendage. After fertilization, the seed capsule splits to the base showing a mass of red, grey or black seeds.

Taxonomy

James Edward Smith described the first species of ''Cautleya'' in 1822; however, he placed them in the genus ''Roscoea'' as ''R. gracilis'' and ''R. spicata''. John Royle first suggested the genus name ''Cautleya'', in honour of Proby Cautley, who was responsible for extensive irrigation works in India under the British Raj. However, in 1839 Royle was persuaded to put his new species into ''Roscoea'', as ''R. lutea''. (''R. lutea'' is now regarded as synonymous with Smith's ''R. gracilis''.) In 1888, Joseph Hooker formalized Royle's name ''Cautleya'', transferring ''R. lutea'' to ''Cautleya lutea''. He separated the genera on the basis that ''Cautleya'' had yellow flowers (although it is now known that some species of ''Roscoea'' have yellow flowers but are distinct from ''Cautleya''). Three other species of ''Cautleya'' were described in 1890, ''C. cathcartii'', ''C. petiolata'' and ''C. robusta''. All are now regarded as synonyms of other species.

A 2002 classification of the family Zingiberaceae, based on molecular phylogenetic analysis, places ''Cautleya'' in the subfamily Zingiberoideae, tribe Zingibereae. In the analysis, it was most closely related to the genus ''Roscoea'', and then to ''Rhynchanthus'', '' Pommereschea'' and ''Hedychium''.

Although related, ''Cautleya'' and ''Roscoea'' can be distinguished in a number of ways. The leaves of ''Cautleya'' have a blade which is separated from the sheath by a stalk ( petiole), sometimes very short, whereas the blades of the leaves of ''Roscoea'' are continuous with the sheath. The bracts surrounding the flowers are coloured in ''Cautleya'', often red, whereas they are not brightly coloured in ''Roscoea''. ''Cautleya'' seeds are red, grey or black, and have only a small aril (or none); those of ''Roscoea'' are green to brown, and have a conspicuous fleshy aril. The way the flowers are arranged is different. In ''Cautleya'', the flowers are spaced out along the flowering spike (inflorescence) to some degree, whereas they are close together in a dense "head" in ''Roscoea''.

Species

, the World Checklist of Selected Plant Families (WCSP) recognized only two species:

*'' Cautleya gracilis'' (Sm.) Dandy ( syns ''C. cathcartii'', ''C. lutea'')
*'' Cautleya spicata'' (Sm.) Baker (syns ''C. petiolata'', ''C. robusta'')

The older ''Flora of China'' recognizes ''C. cathcartii'' as a full species, whereas WCSP treats it as ''C. gracilis'' var. ''robusta'', following Auvray & Newman (2010).

Distribution and habitat

The family Zingiberaceae is mainly tropical in distribution. The unusual mountainous distribution of ''Cautleya'', and the closely related genus ''Roscoea'', may have evolved relatively recently and be a response to the uplift taking place in the area due to the collision of the Indian and Asian tectonic plates in the last 50 million years or so.

''Cautleya gracilis'' var. ''gracilis'' is the most widely distributed, occurring in the Himalayas of north India and Nepal, through mountainous regions in Burma, Yunnan (China) and Thailand to north Vietnam. The other taxa have a similar distribution, but ''C. gracilis'' var. ''robusta'' (syn. ''C. cathcartii'') has not been found in Burma, Thailand or Vietnam, and ''C. spicata'' has not been found in Thailand or north Vietnam.

All generally grow in mountainous regions from about up to almost . Found in the understorey of forests or in moist valleys, they may grow on trees as epiphytes or on the ground in steep rocky locations.

Cultivation

Both species of ''Cautleya'' are in cultivation, along with a number of cultivars and collected forms. When grown in the ground, they are frost-hardy to some degree in climates such as northwest Europe, although a protective covering in winter is advised. A position in at least half shade in a moist, humus-rich soil is recommended. When grown in containers, full protection from frost should be given.

References

External links

* – photographs of ''Cautleya'' in cultivation

{{Taxonbar, from=Q138608

Zingiberoideae
Zingiberales genera
Taxa named by Joseph Dalton Hooker