Carboniferous.html: 29_15CarboniferousForest_U.jpg
Carboniferous forest. Most of the large trees are lycophytes. Tree ferns were also abundant in the “coal forests” of the Carboniferous period, about 300 million years ago. These seedless vascular plant forests eventually became coal and other fossil fuels. The growth of these early forests reduced atmospheric CO₂ levels, leading to global cooling at the end of the Carboniferous.

PlantClades.html: 29_03Charophyceans.jpg
Green algae called charophytes are the closest living algal relatives of land plants.

PlantPhyla.html: 29_07PlantPhylogeny.jpg
Plant evolution. Kingdom Plantae comprises 7 major clades classified into 10 phyla.

alternation.html: 29_05AltGenerat.jpg
Plantae alternation of generations. Multicellular, haploid gametophytes produce haploid gametes. Fusion of egg and sperm form a diploid zygote, which undergoes mitosis to produce the diploid sporophyte. A mature sporophyte may undergo meiosis to produce haploid spores, which can germinate into a haploid gametophytes by mitosis.

apical.html: 29_05Meri.jpg
Apical Meristems. Light and carbon dioxide are above ground, while water and minerals are in the soil.
The elongation of shoots and roots at apical meristems maximize exposure to these resources.

bryophytes.html: 29_09BryophyteDiversity.jpg
Bryophytes lack vascular tissues; these small herbaceous (nonwoody) plants live in moist habitats. The three phyla are: A) Liverworts (Hepatophyta) B) Hornworts (Anthocerophyta) C) Mosses (Bryophyta) Note the small sporophytes growing on the larger gametophytes.

cooling-warming.html: 29_Temp-CO2.gif

embryo.html: 29_05Embryo.jpg
Multicellular, dependent embryos. Multicellular plant embryos develop from zygotes within tissues of the female parent. The parent provides nutrients through placental transfer cells.

eukaryotes.html: 29_04PlantClades.jpg
Kingdom Plantae (Embryophytes) are multicellular, photosynthetic eukaryotes most closely related to the green algae (Chlorophyta).
Plants have adapted to life on dry land.

fern-cycle.html: 29_12FernLifeCycle.jpg
The life cycle of a fern, phylum Pterophyta.

1. Sporangia release spores.
2. Spore develops into a small, bisexual, photosynthetic gametophyte.
3. Gametophyte produces sperm in antheridia and eggs in archegonia.
4. Sperm swim to eggs in archegonia.
5. Zygote develops into large sporophyte.
6. Clusters of sporangia form in sori on modified leaves called sporophylls.

gametangia.html: 29_05Gamet.jpg
Multicellular gametangia in Marchantia (a liverwort). A female gametangium, called an archegonium, produces a single egg. Male gametangia, called antheridia, produce and release sperm into the environment.

lycophyta.html: 29_14VascPlantLycophyta.jpg
Lycophytes (Phylum Lycophyta) Spike mosses are small with simple, scale-like leaves. Quillworts are a single genus that lives in marshy areas. Club mosses have sporophylls (modified leaves with sporangia) clustered into club-shaped cones (strobili).

moss-cycle.html: 29_08MossLifeCycle.jpg
Life cycle of Polytrichum moss, a bryophyte.

1. Spores develop into haploid protonemata.
2. Protonema produce "buds" that undergo mitosis.
3. Buds develop into gametophyte bearing antheridia or archegonia.
4. Sperm swims to egg in archegonium.
5. Fertilized diploid zygote develops into sporophyte embryo.
6. Sporophyte grows a stalk (seta) that emerges from the archegonium.
7. The small sporophyte is dependent on the large gametophyte.
8. Spores develop by meiosis in sporangium (capsule) whose teethlike peristome regulates spore dispersal.

peat.html: 29_Peat.jpg
The acid in peat bogs slows down decay of organic materials.

1. Dead Sphagnum moss can accumulate in deep layers in these bogs and are harvested for fuel and as a soil conditioner.
   
2. This “Tollund Man” has been preserved since the 4th century BC in Denmark.

phyla.html: 29_01ExtantPlantPhyla.jpg
Plant Phyla. Anthophyta (or Angiosperms, the flowering plants) is the most recently evolved, and most diverse, of the 10 plant phyla.

pterophyta.html: 29_14VascPlantPterophyta.jpg

Pterophytes (Phylum Pterophyta)
Ferns have large leaves; the sporophylls bear sori (clusters of sporangia).		Horsetail stems have a gritty texture and some have been used as "scouring rushes" for pots and pans.		Whisk ferns form fused sporangia on stems seen here as yellow knobs.

rhizoids.html: 29_Rhizoids.jpg
The large, photosynthetic, gametophytes of bryophytes contain gametangia and are anchored by rhizoids.

rosette.html: 29_02CharoPlantHomology.jpg
Rosette cellulose–synthesizing complexes. These rose–shaped arrays of proteins, involved in synthesis of cellulose microfibrils of cell walls, are found only in land plants and charophytes, suggesting their close kinship.

sphagnum.html: 29_05Sporan.jpg
Sphagnum, or peat moss, a bryophyte.
Note the “leafy” gametophytes and the smaller sporophytes. The living photosynthetic cells grow on layers of dead water-storing cells, giving the moss a spongy quality.
Peat can be harvested from "peat bogs".

sporangia.html: 29_05Sporan.jpg
Walled spores produced in sporangia. A diploid sporophyte of this Sphagnum (a moss) produces organs called sporangia. The sporangia cells undergo meiosis to generate haploid spores.

vascular.html: 29_UN584SeedlessPhylo.jpg
Vascular plants possess vessels that transport water and nutrients throughout the organism.
Roots enable them to extract water deep within the soil, and the vascular tissues also provide strength to support a larger body mass.