Notes to Accompany "Plant Kingdom Phyla"

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Note 1

Phylum Hepatophyta -- liverworts
Hepatophyta, along with Bryophyta and Anthocerotophyta are sometimes jointly called "bryophytes" since earlier classification systems placed them in a single phylum. All three of these phyla are said to have the gametophyte generation as the "dominant" generation.

In central Texas, large liverworts are fairly common on moist, rocky slopes, on moist tree-trunks, and on boulders in shallow streams. Smaller liverworts are common on soil and tree-trunks.

Note 2
Phylum Bryophyta -- mosses or "true mosses"
Bryophyta, along with Hepatophyta and Anthocerotophyta are sometimes jointly called "bryophytes" since earlier classification systems placed them in a single phylum. All three of these phyla are said to have the gametophyte generation as the "dominant" generation.

In central Texas, true mosses are very often found in a wide variety of habitats, including soil, rocks and trees.

Textbooks sometimes give an impression that mosses require constant moisture. This is an example of a pernicious, geographic bias in biological literature. Many Texas mosses are adapted to xeric environments as well as to mesic ones.

  Note 3
Phylum Anthocerotophyta -- hornworts
Anthocerotophyta, along with Bryophyta and Hepatophyta, are sometimes jointly called "bryophytes" since earlier classification systems placed them in a single phylum. All three of these phyla are said to have the gametophyte generation as the "dominant" generation.

In central Texas, hornworts can often be recognized (with a little practice) as resembling a drop of dark green grease. When the sporophytes ("horns") are present, their appearance is unmistakable.

Note 4 Phylum Psilophyta (or Psilotophyta) -- whisk fern
Psilophyta comprises only two extant genera, Psilotum and Tmesipteris. Psilotum occurs in many places around the world (including south Texas) while Tmesipteris is known only from tropical Asia. In central Texas, Psilotum growing outdoors will survive our mild winters, but not our harsh ones.

Note 5
Phylum Sphenophyta -- sphenophytes or horsetails
Sphenophyta comprises a single extant genus, Equisetum. In central Texas, Equisetum is generally found in soil that is frequently wet. (Austin's Lou Nef Point on Town Lake supports a large population.)

Stems of Equisetum contain deposits of silicon dioxide (glass) which render them unpalatable and strong. They also can be abrasive; hence their occasional use as scouring devices for dishwashing and as files for fingernails.

Equisetum spores have curious arm-like structures called elaters, which twist and turn in response to humidity changes. These elaters are thought to help effect spore dispersal.

Note 6
Phylum Lycophyta (or Lycopodophyta) -- club mosses or ground pines or lycopods
Lycophyta comprises only five or six extant genera (many more extinct taxa) of which three occur in Texas. Lycopodium is common in east Texas, Isoetes occurs on granite outcrops in the hill country; Selaginella occurs throughout the state, although some species are easily mistaken for mosses.

Lycopodium is homosporous--all spores are roughly equal in size. Selaginella and Isoetes are heterosporous--spores are of two distinct sizes, microspores and megaspores.

Note 7
Phylum Pterophyta (or Pteridophyta or Filicinophyta) -- ferns or "true ferns"
Pterophyta is an enormous phylum with dozens of genera in Texas. Although most ferns are homosporous, there are a few heterosporous genera and these heterosporous genera are well represented in central Texas. Central Texas' heterosporous genera of Pterophyta include Marselia, Azolla, and Salvinia.

Fern gametophytes provide students with an excellent opportunity to observe living egg and sperm cells of plants. Most gametophytes, when kept moist, will produce large numbers of gametangia (sex organs) which can be seen easily with a light microscope.

Note 8
Phylum Coniferophyta (or Pinophyta) -- conifers
Coniferophyta comprise a very large phylum of great economic importance. Pinus (pine) is surely its most famous and economically beneficial genus. Numerous genera of conifers can be found in central Texas both growing natively and horticulturally. Of particular note is Juniperus (cedar or red cedar) which causes large-scale allergic reactions among people. (Pollen and seed are produced on different individuals and it is pollen trees that cause human allergies.)

Conifers are heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Conifer seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Coniferophyta are therefore said to be "gymnospermous."

Note 9
Phylum Cycadophyta -- cycads
Cycadophyta comprise a small extant phylum. In Texas, the most commonly encountered genus is Cycas -- commonly called "sago". In central Texas, sago survives most winters, but can be killed in extremely cold ones.

Cycads are heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Cycad seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Cycadophyta are therefore said to be "gymnospermous."

Note 10
Phylum Ginkgophyta -- ginkgo
Ginkgophyta comprises a single extant genus, and once was known only from fossils. However, a population was found growing in China and ginkgo is now widely cultivated as an ornamental tree. They grow satisfactorily in central Texas, but often are slow to establish.

Ginkgophyta is heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Ginkgo seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Ginkgophyta are therefore said to be "gymnospermous".

  Note 11
Phylum Gnetophyta -- gnetophytes
Gnetophyta comprise about three families, one of which occurs in central Texas. Ephedra (Mormon tea) is common in west Texas, but also occurs on limestone in the hill country. This genus (though not the Texas species) is a source of ephedrine.

Gnetophyta is heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Gnetophyta seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Gnetophyta are therefore said to be "gymnospermous."

  Note 12
Phylum Anthophyta (or Magnoliophyta or Angiospermophyta) -- flowering plants
Anthophyta is, by far, the most abundant, familiar, and economically important extant phylum of plants. Features of its reproduction include: specialized strobili called flowers, a covering of seed called a carpel (hence the term, "angiospermous"), a mature carpel technically called a fruit, and a curious cytological process called "double fertilization" which produces both a diploid zygote and a triploid tissue called endosperm.

Almost all human food is directly or indirectly derived from flowering plants. Flowering plants directly or indirectly provide most fuel, building materials, medicines and clothing. Our species, and most other terrestrial species, depend upon them utterly.

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Note 1	Phylum Hepatophyta -- liverworts Hepatophyta, along with Bryophyta and Anthocerotophyta are sometimes jointly called "bryophytes" since earlier classification systems placed them in a single phylum. All three of these phyla are said to have the gametophyte generation as the "dominant" generation. In central Texas, large liverworts are fairly common on moist, rocky slopes, on moist tree-trunks, and on boulders in shallow streams. Smaller liverworts are common on soil and tree-trunks.
Note 2	Phylum Bryophyta -- mosses or "true mosses" Bryophyta, along with Hepatophyta and Anthocerotophyta are sometimes jointly called "bryophytes" since earlier classification systems placed them in a single phylum. All three of these phyla are said to have the gametophyte generation as the "dominant" generation. In central Texas, true mosses are very often found in a wide variety of habitats, including soil, rocks and trees. Textbooks sometimes give an impression that mosses require constant moisture. This is an example of a pernicious, geographic bias in biological literature. Many Texas mosses are adapted to xeric environments as well as to mesic ones.
Note 3	Phylum Anthocerotophyta -- hornworts Anthocerotophyta, along with Bryophyta and Hepatophyta, are sometimes jointly called "bryophytes" since earlier classification systems placed them in a single phylum. All three of these phyla are said to have the gametophyte generation as the "dominant" generation. In central Texas, hornworts can often be recognized (with a little practice) as resembling a drop of dark green grease. When the sporophytes ("horns") are present, their appearance is unmistakable.
Note 4	Phylum Psilophyta (or Psilotophyta) -- whisk fern Psilophyta comprises only two extant genera, Psilotum and Tmesipteris. Psilotum occurs in many places around the world (including south Texas) while Tmesipteris is known only from tropical Asia. In central Texas, Psilotum growing outdoors will survive our mild winters, but not our harsh ones.
Note 5	Phylum Sphenophyta -- sphenophytes or horsetails Sphenophyta comprises a single extant genus, Equisetum. In central Texas, Equisetum is generally found in soil that is frequently wet. (Austin's Lou Nef Point on Town Lake supports a large population.) Stems of Equisetum contain deposits of silicon dioxide (glass) which render them unpalatable and strong. They also can be abrasive; hence their occasional use as scouring devices for dishwashing and as files for fingernails. Equisetum spores have curious arm-like structures called elaters, which twist and turn in response to humidity changes. These elaters are thought to help effect spore dispersal.
Note 6	Phylum Lycophyta (or Lycopodophyta) -- club mosses or ground pines or lycopods Lycophyta comprises only five or six extant genera (many more extinct taxa) of which three occur in Texas. Lycopodium is common in east Texas, Isoetes occurs on granite outcrops in the hill country; Selaginella occurs throughout the state, although some species are easily mistaken for mosses. Lycopodium is homosporous--all spores are roughly equal in size. Selaginella and Isoetes are heterosporous--spores are of two distinct sizes, microspores and megaspores.
Note 7	Phylum Pterophyta (or Pteridophyta or Filicinophyta) -- ferns or "true ferns" Pterophyta is an enormous phylum with dozens of genera in Texas. Although most ferns are homosporous, there are a few heterosporous genera and these heterosporous genera are well represented in central Texas. Central Texas' heterosporous genera of Pterophyta include Marselia, Azolla, and Salvinia. Fern gametophytes provide students with an excellent opportunity to observe living egg and sperm cells of plants. Most gametophytes, when kept moist, will produce large numbers of gametangia (sex organs) which can be seen easily with a light microscope.
Note 8	Phylum Coniferophyta (or Pinophyta) -- conifers Coniferophyta comprise a very large phylum of great economic importance. Pinus (pine) is surely its most famous and economically beneficial genus. Numerous genera of conifers can be found in central Texas both growing natively and horticulturally. Of particular note is Juniperus (cedar or red cedar) which causes large-scale allergic reactions among people. (Pollen and seed are produced on different individuals and it is pollen trees that cause human allergies.) Conifers are heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Conifer seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Coniferophyta are therefore said to be "gymnospermous."
Note 9	Phylum Cycadophyta -- cycads Cycadophyta comprise a small extant phylum. In Texas, the most commonly encountered genus is Cycas -- commonly called "sago". In central Texas, sago survives most winters, but can be killed in extremely cold ones. Cycads are heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Cycad seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Cycadophyta are therefore said to be "gymnospermous."
Note 10	Phylum Ginkgophyta -- ginkgo Ginkgophyta comprises a single extant genus, and once was known only from fossils. However, a population was found growing in China and ginkgo is now widely cultivated as an ornamental tree. They grow satisfactorily in central Texas, but often are slow to establish. Ginkgophyta is heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Ginkgo seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Ginkgophyta are therefore said to be "gymnospermous".
Note 11	Phylum Gnetophyta -- gnetophytes Gnetophyta comprise about three families, one of which occurs in central Texas. Ephedra (Mormon tea) is common in west Texas, but also occurs on limestone in the hill country. This genus (though not the Texas species) is a source of ephedrine. Gnetophyta is heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. Gnetophyta seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. Gnetophyta are therefore said to be "gymnospermous."
Note 12	Phylum Anthophyta (or Magnoliophyta or Angiospermophyta) -- flowering plants Anthophyta is, by far, the most abundant, familiar, and economically important extant phylum of plants. Features of its reproduction include: specialized strobili called flowers, a covering of seed called a carpel (hence the term, "angiospermous"), a mature carpel technically called a fruit, and a curious cytological process called "double fertilization" which produces both a diploid zygote and a triploid tissue called endosperm. Almost all human food is directly or indirectly derived from flowering plants. Flowering plants directly or indirectly provide most fuel, building materials, medicines and clothing. Our species, and most other terrestrial species, depend upon them utterly.