Viola

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Viola

Description

Perennial, rarely annual herbs (in Mal.). Leaves alternate, petioled. Leaves suborbicular to linear-lanceolate, the margin serrate to crenate or subentire, often glandular in indentations. Stipules free or adnate to petiole, persistent, often conspicuous, usually serrate or fimbriate. Flowers bisexual, solitary, axillary, with a pair of bracteoles usually in the upper half of the peduncles. Sepals equal, entire to denticulate or fimbrio-dentate, prolonged into appendages below the point of their insertion, persistent. Petals unequal, the lower saccate or spurred and usually broader than the others, the lateral pair smaller than the upper pair, the lateral petals often, the others more rarely, bearded inside. Fruit a 3-valved lo-culicidal capsule, subtended by dried-up calyx, globose to cylindrical or ellipsoidal, 4-16 mm long; Seeds ∞, usually ellipsoidal, glabrous, with leathery testa, usually with terminal elaiosome.

Distribution

About 400 spp. occurring in temperate regions throughout the world.

Cytology

There has been little cytological work on Malesian violets, and chromosome numbers are available for only 5 of the 16 native species. The counts on Malesian material were all made on plants from New Guinea and were published by and . Chromosome numbers based on extra-Malesian material are indicated in the text.
Cleistogamous flowers. Except for V. tricolor, the species in Malesia produce during some, usually the later, part of the growing season or under abnormal environmental conditions so-called cleistogamous flowers. These have a shorter peduncle, a reduced corolla not expanded beyond the calyx; up to 3 anthers may be aborted and the amount of pollen produced is greatly reduced, while the style is usually much shorter than in chasmogamous flowers and may be much contorted. Such flowers produce plenty of seed, from self-pollination. The variation within species resulting from this sort of reproduction often does not conform to a pattern amenable to formal taxonomic recognition, and may partly explain the multiplicity of names applied to some taxa.
Chasmogamous (i.e. normal, expanding) flowers are essential for the reliable determination of most violets. In the absence of suites of flowering specimens for comparison, fruiting or cleistogamous material can rarely be confidently identified, particularly since, in such material, related species often show convergence in leaf characters.

Notes

With the exception of V. biflora (sect. Dischidium GING.) and the introduced V. tricolor (sect. Melan um GING.), all species occurring in Malesia may be included in sect. Viola (sect. Nomimium GING.).
The separation of V. hederacea and its allies into sect. Erpetion (SWEET) BECKER () does not appear to be justified in view of the intermediates between this and sect. Viola. The various subsectional groupings within sect. Viola (see ) prove impossible to apply effectively and have been omitted in this account. Any useful subsectional treatment must await a monographic revision of the whole genus.

Citation

D. M. MOORE - in Fedde, Rep. 68. 1963
LINNÉ - in Beih. Bot. Centralbl. 1923: 20, 69, 119
LINNÉ - in Bot. Jahrb. 1917: Beibl. 120, 156
LINNÉ - in Beih. Bot. Centralbl. 1918: 15
LINNÉ, Sp. Pl. 1753: 933
LINNÉ - in Beih. Bot. Centralbl. 1917: 373
RIDL. - in J. Bot. 1935: 13
BECKER & MELCHIOR - in E. & P., Pfl. Fam., ed. 2, 21. 1925: 363
MELCHIOR - in Bot. Jahrb. 1929: 368
KORTHALS - in Ned. Kruidk. Arch. 1848: 357
STEEN. - in Bull. Jard. Bot. Btzg. 1934: 258
BOISSIEU & CA-PITAINE - in Bull. Soc. Bot. Fr. 1910: 337
Bl., Cat. Gew. Buitenzorg. 1823: 57
LINNÉ - in Nova Guinea, Bot. 1963: 177
MIQ. - in Ann. Mus. Bot. Lugd.-Bat. 1869: 217
LINNÉ - in Notizbl. Berl.-Dahl. 1934: 205
BECKER - in Beih. Bot. Centralbl. 1916: 208
LIN - in Taiwania. 1950: 269
BURGERS-DIJK - in Miq., Pl. Jungh. 1. 1852: 118
LINNÉ, Bijdr. 1825: 57
OUDEMANS - in Miq., Ann. Mus. Bot. Lugd.-Bat. 3. 1867: 73