Victorin's water-hemlock (Cicuta maculata) COSEWIC assessment and status report: chapter 3

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Name and classification

Scientific name:         Cicuta maculata Linnaeus var. victorinii (Fernald) Boivin

Relevant synonyms:    Cicuta victorinii Fernald

French names:            cicutaire de Victorin, cicutaire maculée variété de Victorin

English names:           Victorin’s water-hemlock, Spotted water hemlock

Family:                         Apiaceae (parsnip family)

The treatment of this variant of Cicuta has been problematic for a number of authors.  Victorin’s water-hemlock (Cicuta victorinii) was first described by Fernald in 1939 on the basis of specimens collected on intertidal beaches at Cap-Rouge and Saint-Laurent on Île d'Orléans by Brother Marie-Victorin (August 9 and 16, 1922). Mathias and Constance (1942) retain this taxon in their synopsis of the American species of Cicuta.  Boivin (1966) considers it to be a variety of Cicuta maculata, a position accepted by Scoggan (1978) and Mulligan (1980).  The latter treats the Cicuta maculata complex and retains the variety on the basis of its fruit with small ribs and swollen intercostal regions.  Gleason and Cronquist (1991) do not recognize the variety victorinii and are of the view that only the variety maculata exists in Eastern North America.  Kartesz (1994) recognized the taxa proposed by Mulligan (1980).  The position taken in this report is to adopt the classification of Mulligan (1980). In his studies, in part with plants grown from seed, Mulligan (1980) recognized two distinct varieties; he also noted that some gradation occurs between the endemic var. victorinii and the typical var. maculata and that ripe fruits are required to readily distinguish between them.

Description

Herbaceous perennial (Figure 1), glabrous, 0.5–2 m high, from a short rootstock.  A bundle of 5–10 oblong tubers grows from the base of the rootstock.  Stem erect, often streaked with purple, hollow except at nodes with leaf stalk clasping the stem and fully encircling it.  Leaves lanceolate to ovate lanceolate, alternate, 10–80 cm long and 4–8 cm wide, each leaf divided into 3 parts composed of leaflets, leaflets linear-lanceolate, finely toothed.  Inflorescence composed of umbels with unequal pedicels; flowers white, small and pedicelled. Fruits: a double achene, light to dark brown (purplish in the field), 3.5 –4 mm long, separating when mature into two seeds, each seed with corky ribs, lateral ribs more prominent than dorsal ribs, which are sometimes absent. A yellowish, oily liquid smelling like parsnips exudes from cut stems and roots.  All plant parts are toxic (Coursol, 2001).

There are three known varieties of water-hemlock in Canada (var. victorinii, var. maculata and var. angustifolia).  According to Legault (1986), var. victorinii is the only variety that occurs in estuarine habitats.  In actual fact, however, the two varieties present in Quebec (var. victorinii and var. maculata) occupy the intertidal zone of the St. Lawrence River.  They can be differentiated on the basis of at least two criteria (Fernald, 1950; Mulligan, 1980; Mulligan and Munro, 1981).

1)      The fruits of var. victorinii are reniform to ovoid-cordate with prominent lateral ribs and obscure dorsal ribs, whereas the fruits of var. maculata are ellipsoid, ovoid or subglobose with light prominent dorsal and lateral ribs alternating with dark ridges.

2)       The leaflets are linear lanceolate in var. victorinii and lanceolate to ovate oblong in var. maculata.

The second criterion is generally unusable, particularly when the two varieties occur together in the estuarine environment.  The only character that can be used to identify var. victorinii with certainty is the mature fruit in early September.  When herbarium specimens harvested before September are dried, the obscure dorsal ribs of the newly collected fruit are sometimes transformed into prominent dorsal ribs after drying.  The herbarium specimens of var. victorinii never have prominent dorsal ribs.

Since the provincial report on the status of Victorin’s water-hemlock was prepared (Coursol, 1999), there has been growing uncertainty regarding the taxonomic validity of Victorin’s water-hemlock.  In 2002, the author observed, in individuals from Cap-Saint-Ignace, some fruits with well-developed dorsal ribs and others with obscure dorsal ribs on the same umbel.  Hybridization of the two varieties must be common in some populations. In the 1996 and 1997 inventories, the author observed that the two varieties often grow in proximity to each other and that individuals occurring at the limit of the upper littoral tend to exhibit characters of var. maculata, whereas individuals submerged for longer periods exhibit characters of var. victorinii.  Detailed studies are required to provide further clarification.