Spermatophytes and Their Salient Features

Spermatophytes are the seed plants. The word covers every plant that makes a seed, which means the conifers, the cycads, the flowering plants, and several extinct groups that no longer exist.

Seed plants are also vascular plants, so they sit inside the tracheophytes, the group that has xylem and phloem. What sets them apart from the ferns and club mosses is not the plumbing but the seed, and everything that has to happen before one can form. This guide lays out the shared features, one at a time.

What "Spermatophyte" Actually Means

A Clade, and an Old-fashioned Name

Modern studies treat the seed plants as a clade: one ancestor and all of its descendants. Spermatophyta is also a traditional formal name, but its rank is not used the same way in every classification system. Both statements are true at once.

The word is often confused with gymnosperm, and that is a mistake. A spermatophyte is any seed plant. Gymnosperms are one part of that group, and flowering plants are the other.

The Seed Ferns Weren't Ferns

Among the extinct seed plants were the pteridosperms, better known as seed ferns. They had fern-like foliage, which is where the name came from, but they reproduced with seeds.

Seed ferns are best treated as an informal, paraphyletic collection rather than one natural group. Paraphyletic means the set leaves out some descendants of its common ancestor, so it is a convenient label for early seed plants rather than a proper branch of the tree.

A fossil frond of Macroneuropteris scheuchzeri. The leaves look like a fern's, but this plant was an early seed plant. Image: James St. John, CC BY 2.0, via Wikimedia Commons

The Salient Features, One by One

A Sporophyte You Can See

The plant you notice is the sporophyte, and it is diploid, meaning each cell carries two sets of chromosomes. It is the dominant generation in every seed plant. The gametophyte is tiny and lives on or inside it.

Two Kinds of Spore on One Plant

Seed plants are heterosporous. They make small microspores, which become male gametophytes, and larger megaspores, which become female gametophytes. Some seedless plants also do this, so heterospory alone is not the seed-plant signature.

The next step is what matters. In a seed plant the megaspore is not released. It stays inside the parent's megasporangium and grows into the female gametophyte there.

The Ovule and the Pollen Grain

That retained megasporangium, wrapped in one or more layers of tissue, is the ovule. The inner part is the nucellus, and the outer layers are the integuments, which later help build the seed coat.

A pollen grain is not a sperm cell. It is the whole male gametophyte, reduced to a couple of cells. It is carried to the ovule, where it grows a pollen tube that delivers sperm cells to the egg.

Because of that tube, fertilization no longer depends on an external film of water. One detail survives from older plants, though. In cycads and Ginkgo the sperm still have tails and swim a short distance near the egg, inside the ovule.

Pollen grains under a scanning electron microscope, colored for contrast. Each grain is a whole male gametophyte, not a single sperm cell. Image: Dartmouth Electron Microscope Facility, public domain, via Wikimedia Commons

Where the Gametophyte Went

Smaller at Every Step

Across land plants the gametophyte has shrunk. In mosses and liverworts the gametophyte is the plant you see, and the sporophyte stays attached to it and depends on it for food.

In ferns the balance flips. The sporophyte becomes the big leafy plant, and the gametophyte is a small, thin structure that in most ferns still lives on its own.

In seed plants the gametophyte loses both size and independence. It is a few cells, it never leaves the parent, and the parent feeds it.

Group	Dominant generation	Ploidy of each stage	What "reduction" means
Bryophytes	Gametophyte	Gametophyte n, sporophyte 2n	The sporophyte is the small dependent stage
Seedless vascular plants	Sporophyte	Gametophyte n, sporophyte 2n	The gametophyte shrinks but often lives free
Seed plants	Sporophyte	Gametophyte n, sporophyte 2n	The gametophyte is tiny and fully dependent

One warning about the word reduction. It describes size, complexity and independence, not ploidy. The gametophyte stays haploid, and it never disappears. A pollen grain is a gametophyte.

How Small Is Small?

In flowering plants the female gametophyte typically has seven cells and eight nuclei, though about 70 percent of species follow that pattern rather than all of them. The male gametophyte is commonly two cells when the pollen is shed, and three after the generative cell divides.

Gymnosperm gametophytes are reduced too, but their cell numbers vary, so no single figure covers them all.

One Life Cycle, Two Patterns

The Sequence

The cycle runs the same way in both groups. A diploid sporophyte makes spores by meiosis. Those spores are haploid. They grow into haploid gametophytes, which make eggs and sperm. Fertilization produces a diploid zygote, and the zygote becomes the embryo inside a seed.

The seed then leaves the parent and, when conditions suit, grows into a new sporophyte. The full loop is sporophyte, spore, gametophyte, fertilization, seed, and back to sporophyte.

One Step Differs Between the Two Groups

Flowering plants add double fertilization. One sperm fertilizes the egg to make the zygote. The second fuses with the central cell and usually starts endosperm, the food store that feeds the embryo.

Gymnosperms do not produce endosperm that way. A gymnosperm seed is usually nourished by haploid tissue from the female gametophyte instead. Some gnetophytes do show a double fertilization event, but it generally does not build the typical embryo-feeding endosperm.

How the Group Is Organised and Where It Came From

Gymnosperms and Angiosperms

Living seed plants split into gymnosperms and angiosperms. The gymnosperms have four groups: conifers, cycads, Ginkgo, and the gnetophytes. Together they account for roughly 1,200 living species.

Angiosperms, the flowering plants, form a single clade and hold roughly 354,000 described species. Add the gymnosperms in and the seed plants come to about 355,000 species.

Group	Everyday members	Approximate living species
Conifers	Pines, firs, spruces, yews	About 650 to 700
Cycads	Cycas, Encephalartos	About 360 to 380
Ginkgo	Ginkgo biloba	One
Gnetophytes	Welwitschia, Ephedra, Gnetum	About 110 to 120
Angiosperms	Grasses, oaks, palms, daisies	About 354,000

Those tallies are approximations. They depend on which names are accepted as valid, how hybrids are counted, and how current the checklist is.

Why Seed Plants Run the Land

Seed plants make up roughly 96 percent of living vascular plant species. That share is an estimate, but the broad picture is not in doubt: forests, grasslands and most of the plants people grow for food are seed plants.

The seed is not the only reason. Vascular tissue and, in many lineages, wood do a lot of the work as well. Not every seed plant is woody, though. Many are herbaceous, and the monocots ancestrally lack the usual cambium that makes conventional wood.

The General Sherman giant sequoia, the largest living tree by trunk volume. Seed plants include the biggest organisms on land. Image: Tuxyso, CC BY-SA 3.0, via Wikimedia Commons

Not All of Them Are Trees

The seed habit reaches far beyond forests. A sunflower is a seed plant, and so is a blade of grass. The group ranges from the largest trees on Earth down to small herbs that complete a life cycle in a single season.

A sunflower is every bit as much a seed plant as a sequoia. That range is why "seed plant" and "tree" are not interchangeable terms. Image: George Chernilevsky, CC BY 4.0, via Wikimedia Commons

From Runcaria to the Coal Swamps

The earliest seed-like fossils are old, and the oldest ones are not quite seeds. Runcaria, from about 385 million years ago, is described as a precursor rather than a finished seed.

By the Late Devonian, plants such as Moresnetia and Elkinsia carried preovules and early seed-plant reproductive structures. The earliest seed-like fossils are generally placed in the Late Devonian, but the fossils are incomplete, so the exact boundary is less certain than a single date suggests.

Seed plants diversified during the Carboniferous, and seed ferns were among the groups present. Gymnosperms then dominated many landscapes through the Triassic and Jurassic.

The Angiosperm Turn

Flowering plants diversified quickly and spread widely from the Early to Mid Cretaceous. Their rise is well documented, though exactly when they first appeared and why they took off are still active research questions.

Key Terms in Plain English

Term	What it means here
Spermatophyte	A seed plant: gymnosperms plus flowering plants.
Tracheophyte	A vascular plant, with xylem and phloem.
Pteridosperm	An extinct seed plant with fern-like leaves; a seed fern.
Clade	One ancestor plus all of its descendants.
Paraphyletic	A group that leaves out some descendants of its ancestor.
Heterospory	Making two sizes of spore, microspores and megaspores.
Megaspore	The spore that becomes the female gametophyte.
Microspore	The spore that becomes the male gametophyte.
Sporophyte	The diploid stage that makes spores; the plant you see.
Gametophyte	The haploid stage that makes eggs and sperm.
Ovule	The megasporangium plus integuments; becomes the seed.
Nucellus	The megasporangium inside an ovule.
Integument	The layer around the nucellus that forms the seed coat.
Pollen grain	The reduced male gametophyte, not a sperm cell.
Pollination	Delivery of pollen to the ovule.
Double fertilization	Two fusions, making a zygote and usually endosperm.
Endosperm	The food tissue of many flowering plant seeds.

Key Takeaways

• A spermatophyte is a seed plant, which includes gymnosperms and angiosperms.
• Seed plants are vascular plants, so they belong to the tracheophytes.
• All seed plants share a dominant sporophyte and two sizes of spore.
• The megaspore stays on the parent, wrapped in an integument, forming an ovule.
• Pollen is the reduced male gametophyte; a pollen tube delivers the sperm.
• The gametophyte shrank but never disappeared, and it is still haploid.

Frequently Asked Questions

Is a spermatophyte the same as a gymnosperm?

No. Spermatophyte means seed plant, which covers gymnosperms and flowering plants. Gymnosperms are only one part of the group.

Does the gametophyte still exist in seed plants?

Yes. It is tiny and depends on the sporophyte. A pollen grain is a male gametophyte, and the female gametophyte develops inside the ovule.

Are all seed plants trees?

No. Seed plants include herbs, grasses and vines as well as trees. Wood is common in some lineages but it is not what defines the group.

Were seed ferns really ferns?

No. Seed ferns were extinct seed plants that happened to have fern-like foliage. The name describes their leaves, not their relationships.

Key references
• OpenStax Biology 2e: Evolution of seed plants
• UC Museum of Paleontology: Introduction to the seed plants
• UC Museum of Paleontology: Fossil record of the seed plants
• Becker et al. (2025): Seed plant review
• Qian et al. (2022): Global vascular plant species counts
• Digital Atlas of Ancient Life: The land plant life cycle

Images: Wikimedia Commons, with the author and license named in each caption. This article is general science education.