Iowa golden saxifrage Chrysosplenium iowense, copyright Tab Tannery.

Belongs within: Hamamelidaceae.
Contains: Heuchera, Saxifraga.

The Saxifragaceae are a diverse group of perennial herbs and subshrubs that are most diverse in temperate and boreal regions.

Misplaced Hawaiians
Published 22 October 2007
Saxifraga oppositifolia, from Wikipedia.

The Saxifragaceae are a small family of about 30 genera of herbaceous plants found in the temperate zones of the world (more in the Northern Hemisphere than the Southern). Many species are found in alpine or arctic habitats. The flowers have a corolla of five separate petals and five conjoined sepals and are often borne in a raceme, while the fruit is generally a dry capsule.

Classification of the Saxifragaceae is a point fraught with difficulty. The brief description I’ve given applies to what was the subfamily Saxifragoideae, to which phylogenetic studies indicate the family should probably be restricted (Soltis & Soltis 1997). Saxifragaceae sensu stricto is then placed in a small order Saxifragales with families such as Crassulaceae, Paeonia and Grossulariaceae. Crassulaceae and Saxifragaceae have both been regarded in the past as members of the subclass Rosidae, and it seems likely that Saxifragales are basal rosids, but other published phylogenies show a little uncertainty about their exact position relative to the rosid-asterid split (for instance, Kårehed [2001] shows Saxifragales as sister to Caryophyllales + Asteridae rather than to Rosidae, but taxon sampling was very low).

Other taxa previously included in Saxifragaceae have been scattered to the winds, settling in a whole range of places within the angiosperm family tree. Most notably, a collection of past saxifragaceans has staked out a position low in the asterid tree as the family Hydrangeaceae. Hydrangeaceae will probably be most familiar as the family including the hydrangeas widely grown as ornamentals (and going by what I’ve heard people saying, seemingly a real love-them-or-hate-them kind of plant). I was always impressed by the story that flower colour in hydrangeas is determined by soil pH—plants in acidic soil produce blue flowers, while alkaline soils give rise to pink flowers.

Kanawao Broussaisia arguta, from Wikipedia.

I had intended to write this post on the genus Broussaisia in Saxifragaceae, but in looking up information for the post I soon discovered that Broussaisia is no longer a saxifragacean as it was listed in Yampolsky & Yampolsky (1922), but a member of Hydrangeaceae. In fact, phylogenetic analysis indicates that Broussaisia (including a single species of Hawaiian shrub, B. arguta, commonly known as the kanawao) is nested within the genus Hydrangea (Hufford et al., 2001). The kanawao is found on all the main islands of Hawaii, and is quite unusual for Hydrangeaceae in producing a fleshy (albeit small) fruit. Go to lemmingreport for an interesting page collecting old reports on the use of kanawao in traditional medicine—apparently the fruit could be used to “bring about conception with a barren woman”. The efficacy of this remedy was such that apparently one could vary the dose to determine whether the child was a boy or a girl… However, the supreme money quote has to be: “It was the way of increasing the population in Hawaii during the old days. … Look at how the numbers of Japanese, Chinese and Filipinos have increased in immigrating in Hawaii. They are not good at settling, but they do take care and know how to increase their numbers”.

Systematics of Saxifragaceae

Characters (from Hickman 1993): Perennial or subshrub from caudex or rhizome, generally more or less hairy. Stem often more or less leafy on lower half, rarely trailing and leafy throughout. Leaves generally simple, basal or sometimes cauline, generally alternate, generally petioled; veins more or less palmate. Inflorescence a panicle, generally more or less scapose. Flowers generally bisexual, generally radial; hypanthium free to more or less fused to ovary; calyx lobes generally 5: petals generally 5, free, generally clawed, generally white; stamens generally 5 or 10; pistils 2 and simple or 1 and compound (chambers 1–2, placentas 2–4, axile or parietal), ovary superior to inferior, sometimes more superior in fruit, styles generally 2. Fruit 2 follicles or 2–4-valved capsule. Seeds generally many, small.

Saxifragaceae [Saxifragoideae]
    |--Saxifragella albowianaNDA05
    `--+--+--Astilbe [Astilboideae]NDA05
       |  |    `--A. taquetiiNDA05
       |  `--+--+--Tanakaea radicansNDA05
       |     |  `--Leptarrhena pyrifoliaNDA05
       |     `--+--+--Telesonix heucheriformisNDA05
       |        |  `--JepsoniaNDA05
       |        |       |--J. heterandra [=J. parryi var. heterandra]H93
       |        |       |--J. malvifoliaH93
       |        |       `--J. parryiNDA05
       |        `--+--Sullivantia oreganaNDA05
       |           `--+--BolandraNDA05
       |              |    |--B. californicaH93
       |              |    `--B. oreganaNDA05
       |              `--BoykiniaNDA05
       |                   |--B. intermediaNDA05
       |                   |--B. majorH93
       |                   |--B. occidentalis [incl. B. elata]H93
       |                   `--B. rotundifoliaNDA05
       `--+--+--+--Tolmiea menziesiiNDA05
          |  |  `--Bensoniella oregonaNDA05 [=Bensonia oreganaH93]
          |  `--+--Elmera racemosaNDA05
          |     `--+--TiarellaNDA05
          |        |    |--T. polyphyllaO88
          |        |    `--T. trifoliataH93
          |        |         |--T. t. var. trifoliataH93
          |        |         `--T. t. var. unifoliataH93
          |        `--+--HeucheraNDA05
          |           `--+--Tellima grandifloraNDA05
          |              `--MitellaNDA05
          |                   |--M. breweriH93
          |                   |--M. caulescensH93
          |                   |--M. diphyllaJ23
          |                   |--M. diversifoliaNDA05
          |                   |--M. nudaNDA05
          |                   |--M. ovalisH93
          |                   |--M. pentandraNDA05
          |                   `--M. trifidaH93
          `--+--+--+--Astilboides tabularisNDA05
             |  |  |--Darmera peltataNDA05 [=Peltiphyllum peltatumH93]
             |  |  `--Rodgersia pinnataNDA05
             |  `--+--Mukdenia rosiiNDA05
             |     `--BergeniaNDA05
             |          |--B. cordifoliaJK80
             |          `--B. purpurascensO88
                `--+--Peltoboykinia tellimoidesNDA05
                   `--Chrysosplenium Linnaeus 1753NDA05, KC01
                        |--C. carnosumO88
                        |--C. forrestiiO88
                        |--C. glechomifoliumH93
                        |--C. iowenseNDA05
                        |--C. nepalenseO88
                        |--C. nudicauleO88
                        |    |--C. n. var. nudicauleO88
                        |    `--C. n. var. intermediumO88
                        |--C. tenellumO88
                        `--C. uniflorumO88
Saxifragaceae incertae sedis:
  Suksdorfia ranunculifoliaH93
    |--L. affine [incl. L. affine ssp. mixtum, L. tripartita]H93
    |--L. bolanderi [incl. L. scabrella]H93
    |--L. cymbalariaH93
    |--L. glabrum [incl. L. bulbiferum]H93
    |--L. heterophyllumH93
    |--L. maximumH93
    |--L. parviflorumH93
    |    |--L. p. var. parviflorumH93
    |    `--L. p. var. trifoliatumH93
    `--L. tenellum [incl. L. breviloba, L. rupicola]H93
  Saxifragopsis fragarioides [=Saxifraga fragarioides]H93
  Saxifragispermum spinosissimum Reid & Chandler 1933CBH93
  Elmeria Ridl. 1905KC01
    |--M. engleri (Dalla Torre) Galasso, Banfi & Soldano in Banfi, Galasso & Soldano 2005 (see below for synonymy)BGS05
    |--‘Saxifraga’ gageanaWO88
    |--‘Saxifraga’ pallidaWO88
    `--M. stellaris (L.) Galasso, Banfi & Soldano in Banfi, Galasso & Soldano 2005 (see below for synonymy)BGS05

Micranthes engleri (Dalla Torre) Galasso, Banfi & Soldano in Banfi, Galasso & Soldano 2005 [=Saxifraga engleri Dalla Torre 1882, S. stellaris ssp. engleri; incl. S. stellaris ssp. alpigena, S. stellaris ssp. robusta]BGS05

Micranthes stellaris (L.) Galasso, Banfi & Soldano in Banfi, Galasso & Soldano 2005 [=Saxifraga stellaris L. 1753]BGS05

*Type species of generic name indicated


[BGS05] Banfi, E., G. Galasso & A. Soldano. 2005. Notes on systematics and taxonomy for the Italian vascular flora. 1. Atti Soc. It. Sci. Nat. Museo Civ. Stor. Nat. Milano 146 (2): 219–244.

[CBH93] Collinson, M. E., M. C. Boulter & P. L. Holmes. 1993. Magnoliophyta (‘Angiospermae’). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 809–841. Chapman & Hall: London.

[H93] Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).

Hufford, L., M. L. Moody & D. E. Soltis. 2001. A phylogenetic analysis of Hydrangeaceae based on sequences of the plastid gene matK and their combination with rbcL and morphological data. International Journal of Plant Sciences 162 (4): 835–846.

[J23] James, E. 1823. Account of an Expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819 and ’20, by order of the Hon. J. C. Calhoun, sec’y of war: under the command of Major Stephen H. Long. From the notes of Major Long, Mr. T. Say, and other gentlemen of the exploring party vol. 1. H. C. Carey & I. Lea: Philadelphia.

[JK80] John, J., & K.-P. Kolbe. 1980. The systematic position of the “Theales” from the viewpoint of serology. Biochemical Systematics and Ecology 8: 241–248.

Kårehed, J. 2001. Multiple origin of the tropical forest tree family Icacinaceae. American Journal of Botany 88 (12): 2259–2274.

[KC01] Kirk, P. M., P. F. Cannon, J. C. David & J. A. Stalpers. 2001. Ainsworth & Bisby’s Dictionary of the Fungi 9th ed. CAB International: Wallingford (UK).

[NDA05] Nickrent, D. L., J. P. Der & F. E. Anderson. 2005. Discovery of the photosynthetic relatives of the “Maltese mushroom” Cynomorium. BMC Evolutionary Biology 5: 38.

[O88] Ohba, H. 1988. The alpine flora of the Nepal Himalayas: an introductory note. In: Ohba, H., & S. B. Malla (eds) The Himalayan Plants vol. 1. The University Museum, University of Tokyo, Bulletin 31: 19–46.

[P92] Poinar, G. O., Jr. 1992. Life in Amber. Stanford University Press: Stanford.

Soltis, D. E., & P. S. Soltis. 1997. Phylogenetic relationships in Saxifragaceae sensu lato: a comparison of topologies based on 18S rDNA and rbcL sequences. American Journal of Botany 84 (4): 504–522.

[YY22] Yampolsky, C., & H. Yampolsky. 1922. Distribution of sex forms in the phanerogamic flora. Bibliotheca Genetica 3: 1–62.

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