Viola (plant)

Viola (US /vaɪˈoʊlə/ and UK /ˈvaɪ.ələ/) is a genus of flowering plants in the violet family Violaceae. It is the largest genus in the family, containing between 525 and 600 species. Most species are found in the temperate Northern Hemisphere, however some are also found in widely divergent areas such as Hawaii, Australasia, and the Andes.

Some Viola species are perennial plants, some are annual plants, and a few are small shrubs. A large number of species, varieties and cultivars are grown in gardens for their ornamental flowers. In horticulture the term "pansy" is normally used for those multi-coloured, large-flowered cultivars which are raised annually or biennially from seed and used extensively in bedding. The terms "viola" and "violet" are normally reserved for small-flowered annuals or perennials, including the species.

Description

Viola typically have heart-shaped, scalloped leaves, though a number have palmate leaves or other shapes. The vast majority of Viola species are herbaceous, and a substantial number are acaulescent in habit - meaning they lack any noticeable stems and the foliage and flowers appear to rise from the ground; the remaining species have short stems with foliage and flowers produced in the axils of the leaves. The simple leaves of plants with either habit are arranged alternately; the acaulescent species produce basal rosettes. Plants always have leaves with stipules that are often leaf-like.

Viola

The viola (/viˈoʊlə/;Italian pronunciation: [ˈvjɔːla]) is a bowed string instrument. It is slightly larger than a violin in size and has a lower and deeper sound than a violin. Since the 18th century it has been the middle voice of the violin family, between the violin (which is tuned a perfect fifth above it) and the cello (which is tuned an octave below it).

Music that is written for the viola differs from that of most other instruments, in that it primarily uses the alto clef, which is otherwise rarely used. Viola music employs the treble clef when there are substantial sections of music written in a higher register.

The viola occasionally has a major role in orchestral music. In the earlier part of the 20th century, more composers began to write for the viola, encouraged by the emergence of specialized soloists such as Lionel Tertis. Englishmen Arthur Bliss, York Bowen, Benjamin Dale, and Ralph Vaughan Williams all wrote chamber and concert works for Tertis. William Walton, Bohuslav Martinů and Béla Bartók wrote well-known viola concertos. Paul Hindemith wrote a substantial amount of music for viola. In the latter part of the 20th century a substantial repertoire was produced for the viola.

Plant

Plants, also called green plants, are multicellular eukaryotes of the kingdom Plantae. They form an unranked clade Viridiplantae (Latin for green plants) that includes the flowering plants, conifers and other gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses and the green algae. Green plants excludes the red and brown algae, the fungi, archaea, bacteria and animals.

Green plants have cell walls with cellulose and obtain most of their energy from sunlight via photosynthesis by primary chloroplasts, derived from endosymbiosis with cyanobacteria. Their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are also characterized by sexual reproduction, modular and indeterminate growth, and an alternation of generations, although asexual reproduction is also common.

Precise numbers are difficult to determine, but as of 2010, there are thought to be 300–315 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants (see the table below). Green plants provide most of the world's molecular oxygen and are the basis of most of the earth's ecologies, especially on land. Plants that produce grains, fruits and vegetables form mankind's basic foodstuffs, and have been domesticated for millennia. Plants are used as ornaments and, until recently and in great variety, they have served as the source of most medicines and drugs. The scientific study of plants is known as botany, a branch of biology.