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I. Taxonomy
Violets are dicotyledonous plants of the Subclass Dilleniidae, order Violales, family Violaceae, genus Viola (Cronquist, 1981). Viola sororia is only one of approximately 400 Viola species (Cronquist, 1981).

Viola sororia Willd., the state flower of New Jersey (NJ Statutes Annotated) is a member of the section Nomimium Ging., subsection Plagiostigma Godr. (Canne, 1987; McKinney, 1992).

McKinney (1992) divides Viola sororia Willd. into four varieties, V. sororia var. sororia (previously V. sororia), V. sororia var. affinis (previously V. affinis), V. sororia var. missouriensis (previously V. missouriensis), V. sororia var. novae-angliae (previously V. novae-angliae). The four varieties differ in leaf shape and dimensions, pubescence [leaf hairs], time of sexual reproduction, among other traits (McKinney, 1992). In addition there is a color form of V. sororia known as V. sororia f. priceana (McKinney, 1992), commonly called the confederate violet (Fuller, 1990). Several named cultivars exist such as V. sororia cv. Albaflora, V. sororia cv. Freckles, and V. sororia cv. Rubra. I have occasionally seen the misnomers V. soraria and V. sororaria used in place of V. sororia.

Common names for V. sororia var. sororia include common blue violet (Grimm, 1993), common meadow violet (NJ Statutes Annotated), hooded blue violet (Grimm, 1993), sister violet (Fuller, 1990), and woolly blue violet (Peterson and McKenny, 1968). V. sororia var. missouriensis [V. missouriensis] is sometimes called the Missouri violet (Peterson and McKenny, 1968); V. sororia var. affinis [V. affinis] is Le Conte's violet (Peterson and McKenny, 1968); V. sororia var. novae-angliae [V. novae-angliae] is the New England Blue Violet (Peterson and McKenny, 1968).

II. Vegetative Morphology, Growth and Development
Violet seeds have large straight embryos and flat cotyledons inside an abundant, soft-fleshy, oily endosperm (Cronquist, 1981; Martin, 1946). The seed coat has an aril which is attractive to ants and is therefore an elaiosome (Johri, 1984).

The fresh weight of seeds is not a significant factor in the growth rate or final size of V. sororia var. sororia plants, but the survival rate of the seedlings is size dependent (Solbrig et al., 1980).

The plant is a perennial with thick, horizontal, fleshy rhizomes and ascending to erect leaves. Lateral branches easily detach for asexual reproduction and large clones can form (Holm, 1932; McKinney, 1992; Valentine, 1962). All leaf blades are uncut. Most plants are not heavily pubescent (Holm, 1932; McKinney, 1992). At least in V. sororia var. affinis, stomata are equally numerous on either side of the leaf (Holm, 1932).

The rate of rhizome production is positively correlated to the dry weight of the plants (Antlfinger et al., 1985). The growth rate of small plants is higher than that of large plants, probably due to the partitioning of resources into reproductive structures (Antlfinger et al., 1985). Plants can respond to reduced lighting, by increasing leaf size and petiole length while reducing their relative rate of growth (Antlfinger et al., 1985).

III. Sexual Reproduction
V. sororia is a "stemless violet", that is their flowers arise from rhizomes via long peduncles. Sexual reproduction can occur via showy chasmogamous flowers which can both out cross and self pollinate, or cleistogamous flowers which self pollinate (McKinney, 1992; Valentine, 1962). Most seed set is the result of self pollination. Fruits are capsules and seeds are explosively ejected or dispersed by ants.

Plants need to reach a dry weight of at least 0.15 g to produce appreciable amounts of seed from cleistogamous flowers and the seed production is positively correlated to the dry weight of the plants (Antlfinger et al., 1985; Solbrig et al., 1980). Cleistogamous seed production and rhizome production are negatively correlated to each other.

IV. Geographic Distribution
V. sororia as defined by McKinney (1992), is widely found across the United States and Canada. Each subspecies has a smaller distribution. V. sororia var. sororia is found in the mid to eastern United States and southern Canada, V. sororia var. affinis, is found in western and extreme northeastern sections of the United States and Canada, V. sororia var. missouriensis is found in the eastern United States, and V. sororia var. novae-angliae is found in Minnesota, Wisconsin, Maine, Quebec and New Brunswick. Of the four varieties only V. sororia var. sororia and V. sororia var. missouriensis are native to New Jersey (McKinney, 1992).

V. sororia var. sororia is found in drier areas than the other four subspecies and often in waste grounds (McKinney, 1992) or on the forest floors of open woods in semi-shaded conditions (McKinney, 1992).

V. Genetics
The four varieties of V. sororia as defined by Mc Kinney (1992) show a remarkable level of phenotypic variation. Flower colors include lavender, dull red, pale violet, grayish blue, and blue-violet (Coon, 1977). Although all V. sororia varieties have uncut leaf blades the shapes of the blades are highly variable (Mc Kinney, 1992). Bloom and fruiting periods range from March to May for V. sororia var. missouriensis, and from May to July for V. sororia var. affinis (Mc Kinney, 1992). The height of V. sororia varieties can range from 5 to 30 cm (Coon, 1977; McKinney, 1992). There is significant variation in seed germination rates as well as the final percentage of seed germination (Solbrig et al., 1980).

Antlfinger et al. (1985) showed that mean leaf area, mean leaf width, mean petiole length, total leaf area, total petiole length, above ground biomass, and the total number of seeds, capsules, and rhizomes produced by the plants were heritable traits with heritability values between 9% and 39%.

Hybridization occurs among the various species of acaulescent blue violets because there are few reproductive barriers (McKinney, 1992)

V. sororia has a chromosome number of 2n = 54 (Canne, 1987; Clausen, 1929; McKinney, 1992).

VI. Plant Culture
The general culture of violets, including pest control, disease control and propagation are described in Coon (1977), Farrar (1989), and Fuller (1990). Specific techniques for growing and propagating V. sororia under controlled conditions are given in Antlfinger et al. (1985), Simon et al. (1985), Solbrig (1981) and Solbrig et al. (1980).

VII. References
Antlfinger, A.E., W.F. Curtis, O.T. Solbrig (1985) Environmental and genetic determinants of plant size in Viola sororia. Evolution 39: 1053-1064

Canne, J.M. (1987) Determinations of chromosome numbers in Viola (Violaceae). Canadian Journal of Botany 65: 653-655

Clausen J. (1929) Chromosome number and relationship of some north American species of Viola. Annals of Botany XLIII: 741-764

Coon N. (1977) The complete book of violets. A.S. Barnes & Co., Inc. Cranberry, NJ. 147 pp.

Cronquist, A. (1981) An Integrated System of Classification of Flowering Plants. Columbia University Press., New York. 1262 pp.

Farrar E. (1989) Pansies, Violas and Sweet Violets. Hurst Village Publishing, Taunton, UK. 79 pp.

Fuller, R. (1993) Pansies, Violas and Violettas. The Complete Guide. The Crowood Press, Trowbridge, Wiltshire, UK. 233 pp.

Grimm, W.C. (1993) The Illustrated Book of Wildflowers and Shrubs. Stackpole Books, Mechanicsburg, PA. 637 pp.

Holm, T. (1932) Comparative studies of north American violets. Beihefte zum Botanischen Centralblatt. 2. Abteilung, Systematik, Pflazengeographie, angewandte Botanik 2: 135-182

Johri, B.M. (editor) (1984) Embryology of Angiosperms. Springer-Verlag, Berlin

Martin, A.C. (1946) The Comparative Internal Morphology of Seeds. The American Midland Naturalist 36: 513-660

McKinney, L.E. (1992) A taxonomic revision of the aculescent blue violets (Viola) of North America. SIDA, Botanical Miscellany, No. 7, Botanical Research Institute of Texas, Inc., 60 pp.

Valentine, D.H. (1962) Variation and evolution in the Genus Viola. Preslia 34: 190-206

New Jersey Statutes Annotated. Title 52. State Government, Departments and Officers. (1986) Violet designation as state flower. 52:9AA-1. West Publishing Co., St. Paul, Minnesota., p 77

Peterson R.T. and M. McKenny (1968) A field guide to wildflowers of northeastern and northcentral north America. The Peterson Field Guide Series. Houghton Mifflin Co., Boston. 420 pp.

Simon, J.-P., C. Charest, M.-J. Peloquin (1985) Thermal adaptation and acclimation of higher plants at the enzyme level: Thermostability of NAD malate dehydrogenase in three species of Viola. Journal of Ecology 73: 397-406

Solbrig, O.T. et al. (1981) Studies on the population biology of the genus Viola . II The effect of plant size on fitness in Viola sororia. Evolution 35: 1080-1093

Solbrig, O.T. et al. (1980) The population biology of the genus Viola . I The demography of Viola sororia. Evolution 35: 1080-1093