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Sium

Higher Taxonomy
Family: Apiaceae (Umbelliferae)View DescriptionDichotomous Key

Common Name: CARROT FAMILY
Habit: Annual to perennial herb [shrub, tree], generally from taproot. Stem: generally +- scapose, generally ribbed, hollow. Leaf: basal and generally cauline, generally alternate; stipules generally 0; petiole base generally sheathing stem; blade generally much dissected, occasionally compound. Inflorescence: umbel or head, simple or compound, generally peduncled; bracts present in involucres or 0; bractlets generally present in "involucels". Flower: many, small, generally bisexual (or some staminate), generally radial (or outer bilateral); calyx 0 or lobes 5, small; petals 5, free, generally ovate or spoon-shaped, generally incurved at tips, generally +- ephemeral; stamens 5; pistil 1, ovary inferior, 2-chambered, generally with a +- conic, persistent projection or platform at tip subtending 2 free styles. Fruit: 2 dry, 1-seeded halves (= mericarps), separating from each other but generally +- persistent to central axis; ribs on halves 5, 2 marginal, 3 to back; oil tubes 1--several per interval between ribs.
Genera In Family: 300 genera, 3000 species: +- worldwide, especially temperate; many cultivated for food or spice (e.g., Carum, caraway; Daucus; Petroselinum); Bupleurum lancifolium Hornem. is historical garden weed; some toxic (e.g., Conium). Note: Mature fruit generally critical in identification, shape given in outline. Hydrocotyle moved to Araliaceae. Petroselinum crispum (Mill.) A.W. Hill is a waif.
eFlora Treatment Author: Lincoln Constance & Margriet Wetherwax, except as noted
Scientific Editor: Douglas H. Goldman, Bruce G. Baldwin.

Sium
Habit: Perennial herb, glabrous; roots clustered, fibrous or +- tuberous. Stem: erect or ascending, branched. Leaf: blade oblong to ovate, 1-pinnate, occasionally 2-pinnate when submerged, leaflets distinct, serrate, irregularly cut to pinnately lobed. Inflorescence: umbels compound, generally opposite a leaf; bracts, bractlets leaf-like, generally reflexed, conspicuous; rays, pedicels many, spreading-ascending. Flower: occasionally +- bilateral; calyx lobes 0 or minute; petals wide, white, narrowed at tips, outer +- > others. Fruit: ovate to round, +- compressed side-to-side; ribs prominent, +- equal, corky; oil tubes 1--3 per rib-interval; fruit axis entire or divided to base, adhering to fruit halves or not. Seed: face flat. Chromosomes: 2n=12.
Species In Genus: +- 10 species: North America, Eurasia, Africa. Etymology: (Greek: for an aquatic member of family)
eFlora Treatment Author: Lincoln Constance & Margriet Wetherwax
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Citation for this treatment: Lincoln Constance & Margriet Wetherwax 2016. Sium, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=10223, accessed on April 28, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on April 28, 2016.