FNA: Portulacaceae vs. Montia

Distribution

Primarily Southern Hemisphere; poorly represented in Eurasia

Worldwide

Discussion

Genera 20–30, species ca. 500 (9 genera, 91 species in the flora).

The eastern New World species of Portulacaceae seem to have a closer relationship with the African species, and the western New World species a closer one with the Australian species, than the two New World groups have with each other to each other.

The outer perianth segments, referred to herein as sepals, are held by some (e.g., T. Eckardt 1976) to be modified bracteoles, the petals then representing the true sepals. However, the traditional interpretation, adopted here and in most North American floras, still finds current support (R. C. Carolin 1987). A comparable situation prevails with respect to the cauline leaves in Claytonia and other genera, which are widely interpreted to be foliaceous bracts (R. C. Carolin 1987); here again, as is appropriate in a descriptive context, the traditional terminology is employed. In Talinopsis and Portulaca, the stipular nature of the nodal or axillary hairs also has been a matter of discussion. The question was revisited by R. Geesink (1969), who denied their stipular origin.

The relationships of the family are not a matter of dispute (A. Cronquist 1981; R. C. Carolin 1987); the same cannot be said for the relationships and delimitations of the genera, which have always been labile. They are, at present, the subject of active research, which has led to the current acceptance of Phemeranthus and Cistanthe. Changes in the generic classification are discussed in the treatments of the genera concerned.

Because of the uncertain relationships, the genera and species are listed alphabetically.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species 12 (8 in the flora).

The classification of Montia is in transition. It is widely recognized that the genus as traditionally treated is a rather disparate assemblage of species, albeit closely related. Several segregate genera have been described, but as R. C. Carolin (1993) has observed, “while some are almost certainly recognizable at the generic level, the others probably less certainly.” With the current legitimate uncertainty, it is appropriate to treat Montia here in the broad, traditional sense. To do otherwise is to give the impression that we know more about the relationships of the species than is actually the case.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key

1. Ovary half-inferior to inferior	Portulaca
1. Ovary superior	→ 2
2. Subshrubs; stem nodes pubescent	Talinopsis
2. Herbs; stem nodes glabrous	→ 3
3. Capsule dehiscence circumscissile, valves longitudinally dehiscent from base	→ 4
3. Capsule dehiscence not circumscissile, valves longitudinally dehiscent from apex	→ 5
4. Petals 25-40 mm; seeds strophiolate; nc Washington to extreme sc British Columbia	Cistanthe
4. Petals 4-26 mm (15-35 mm in Lewisia rediviva); seeds estrophiolate; more widespread	Lewisia
5. Stigmas 2; capsule valves 2	Cistanthe
5. Stigmas 1 or 3; capsule valves 2-3	→ 6
6. Sepals mostly deciduous; inflorescences not appearing secund; leaves articulate at base, attachment points round, not clasping; capsule valves wholly or partly deciduous	→ 7
6. Sepals persistent; inflorescences somewhat to markedly secund (at least distally); leaves not articulate at base, attachment points linear, somewhat to markedly clasping; capsule valves not deciduous	→ 8
7. Leaf blades broadly planate, 1-7 cm wide; capsules tardily dehiscent, valves or portions of them sometimes persistent; exocarp and endocarp distinctly differentiated, sometimes separating; seeds minutely tuberculate or striolate, strophiolate, not covered by membrane	Talinum
7. Leaf blades terete or semiterete, 1-3 mm wide, (narrowly planate, 1[-2] cm wide in Phemeranthus aurantiacus); capsules promptly dehiscent, valves deciduous; exocarp and endocarp not evidently differentiated and not separating; seeds smooth, rugulose, or distinctly ridged, estrophiolate, covered by thin, fleshy to chartaceous membrane	Phemeranthus
8. Ovules and seeds (1-)7-40	→ 9
8. Ovules 3 or 6; seeds 1-6	→ 10
9. Leaves and sepals sometimes with elongate, unicellular hairs; sepals distinctly angular or keeled; capsule valves reflexed after dehiscence, margins markedly involute	Calandrinia
9. Leaves and sepals without elongate, unicellular hairs; sepals not distinctly angled or keeled; capsule valves not reflexed after dehiscence, margins not markedly involute	Cistanthe
10. Cauline leaves 2 (rarely 3 in whorl), distinct or partially or completely connate; ovules 3 or 6	Claytonia
10. Cauline leaves more than 2, distinct; ovules 3	Montia

1. Leaves opposite, never alternate or borne on flowering stems	→ 2
1. Leaves alternate or secund, or borne on flowering stems	→ 3
2. Plants annual or biennial, never bulbiferous; stems prostrate or decumbent; stamens 3	M. fontana
2. Plants perennial, usually bulbiferous; stems erect; stamens 5	M. chamissoi
3. Petals 6-15 mm, always present; plants rhizomatous or stoloniferous, often bulbiferous	→ 4
3. Petals 0.7-6 mm, sometimes absent; plants not rhizomatous, stoloniferous, or bulbiferous	→ 5
4. Plants not bulbiferous; leaves not in basal rosette; inflorescences 1-bracteate; Alaska, Yukon	M. bostockii
4. Plants often bulbiferous; leaves in basal rosettes; inflorescences leafy; Pacific coast, cordillera of w North America	M. parvifolia
5. Leaf blades 10-40 mm wide; clasping leaf sheaths absent; stamens 5	M. diffusa
5. Leaf blades 0.5-4 mm wide; clasping leaf sheaths present; stamens (2-)3-5	→ 6
6. Petals often absent; inflorescences axillary	M. howellii
6. Petals present; inflorescences terminal	→ 7
7. Flowers 2-8; seeds 1.2-2.6 mm; stems 2-30 cm	M. linearis
7. Flowers 4-12; seeds 0.8-1.2 mm; stems 1-10 cm	M. dichotoma