Families of Vascular Plants - EEB 337H

Selected vascular plant families of Ontario

(plus selected exotic families of economic or other importance)


Together with the non-vascular green plants (Bryophyta), all of the groups listed below share a common life cycle involving alternation of gamete-producing and spore-producing generations that becomes progressively modified, as described below.

Pteridophyta or "Vascular Cryptogams"

Free-living gametophyte, with microscopic structures for sexual reproduction; motile sperm.

Seed Plants; "Spermatophyta" or "Phanerogams"

Gametophyte retained within tissue of parent sporophyte (=ovule; with development of embryo sporophyte, =seed); macroscopic sporophyte structures associated with sexual reproduction.

Ovules naked; "Gymnosperms"

  • Cycadophyta; sperm motile
  • Ginkgophyta; sperm motile
  • Pinophyta ("Coniferophyta"); microgametophyte (pollen grain) germinates to form pollen tube, two (out of six or more) nuclei function as "sperm"
  • Gnetophyta; microgametophyte (pollen grain) germinates to form pollen tube, two nuclei (out of four) function as "sperm"

Ovules enclosed; "Angiosperms"

Vascular tissues with vessels in most but not all cases (click HERE for a page illustrating the contrast between gymnosperm and angiosperm wood); microgametophyte (pollen grain) germinates to form pollen tube, two nuclei (out of three) function as "sperm" in double fertilization. Nine families treated in detail:

Two cotyledons; Magnoliopsida; "Dicots"

This has been shown to be a paraphyletic group because as defined (by the presence of two cotyledons in the embryo), it excludes the Liliopsid (monocot) clade (see discussion and tree below) and thus includes some, but not all, of the descendants of the common ancestor of the flowering plants. It comprises...
Magnoliidae: eight orders, including
  • Magnoliales (Magnoliaceae; Liriodendron, Magnolia, Michelia)
  • Laurales (Lauraceae; Sassafras)
  • Aristolochiales (Aristolochiaceae; Asarum)
  • Ranunculales (Ranunculaceae)
  • Papaverales (Papaveraceae; Sanguinaria, Stylophorum)
Hamamelididae: 11 orders, including
  • Hamamelidales (Platanaceae; Platanus)
  • Urticales (Ulmaceae; Ulmus, Celtis)
  • Juglandales (Juglandaceae; Carya, Juglans)
  • Fagales (Fagaceae; Fagus, Quercus) (Betulaceae; Alnus, Betula, Carpinus, Corylus, Ostrya)
Caryophyllidae: three orders, including
  • Caryophyllales (Cactaceae; Opuntia)
Dilleniidae: 13 orders, including
  • Ericales (Ericaceae sensu lato)
  • Malvales (Tiliaceae; Tilia)
  • Nepenthales (Sarraceniaceae; Sarracenia)
  • Capparales (Capparaceae, Brassicaceae)
Rosidae: 18 orders, including
Asteridae: 11 orders, including

One cotyledon; Liliopsida; "Monocots"

In contrast, the monophyly of the Liliopsida is supported by several morphological synapomorphies as well as by DNA sequence data. The group comprises...
Alismatidae: (four orders)
 
Arecidae: five orders, including
  • Arecales (Arecaceae, i.e. palms)
  • Arales (Araceae)
Commelinidae: seven orders, including
Zingiberidae:
Liliidae:

The classification above, and the diagram of flowering plant relationships at the right (it appears on the individual family pages), are taken from the 1988 book by Arthur Cronquist. This classification is a modern descendant of the ideas of the late 19th c. American taxonomist, C. E. Bessey. It implies that the Magnoliopsida ("dicots") and Liliopsida (monocots) are both monophyletic groups, something that not quite 20 years later is no longer supported by the evidence that has increasingly become available (see below).

According to Bessey, the flowers of modern Ranunculaceae were reminiscent of the extinct, Mesozoic cycad-like Bennettitales from which Bessey believed the flowering plants arose. In these plants the reproductive structures consisted of cone-like strobili with spirally arranged bracts, microsporophylls, and megasporophylls. Bessey supposed that these organs became transformed into, respectively, the perianth, stamens, and pistils of flowering plants. The Ranunculales ("Ranales") were thus seen by Bessey as the most primitive modern plants, representative of ancestors from which all other flowering plants arose.

Studies of Angiosperm phylogeny based on DNA sequence data, and increasingly also incorporating morphological and fossil data, have led to hypotheses that can be summarized by trees like the one below (click HERE to see earlier versions of this now largely agreed-upon tree that were derived from different sources of molecular data).

 

Cronquist bubblegram  
Angiosperm phylogeny (APW)    

 

Ontario representation of the major clades of flowering plants:

 

A gallery of selected synapomorphies

vessels - Acer stem in tangential section vessels - Acer wood maceration Platanus pollen grain Medeola virginiana rhizomes Asparagus stem in t.s. parallel venation - Streptopus Aronia melanocarpa Acer negundo pollen grains
Vessels in the wood of Acer; absent in Amborella. Photos by Julie Kang. Columellate pollen grain of Platanus; portion of photo by Darlene DeMason, courtesy of Botanical Society of America Adventitious roots on rhizomes of Medeola virginiana. Photo by Mary Ferguson.

Asparagus stem in transverse section showing s cattered vascular bundles. Photo by N. G. Dengler.

Parallel venation in leaves of Streptopus roseus. Photo by Mary Ferguson. Stamens with distinct anther and
filament in Aronia melanocarpa.
Photo by Mary Ferguson.
Pollen grains of Acer negundo showing three colpi; portion of photo by Marshall Sundberg, courtesy of Botanical Society of America

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Please send your comments to tim.dickinson@utoronto.ca; last updated 19-Oct-2009