1. Introduction to the Spermatophytes
The seed plants
The spermatophytes, which means "seed plants", are some of the most important organisms on Earth. Life on land as we know it is shaped largely by the activities of seed plants. Soils, forests, and food are three of the most apparent products of this group.
Seed-producing plants are probably the most familiar plants to most people, unlike mosses, liverworts, horsetails, and most other seedless plants which are overlooked because of their size or inconspicuous appearance. Many seed plants are large or showy. Conifers are seed plants; they include pines, firs, yew, redwood, and many other large trees. The other major group of seed-plants are the flowering plants, including plants whose flowers are showy, but also many plants with reduced flowers, such as the oaks, grasses, and palms.
This large and important group appeared early in the evolution of vascular plants, and throughout the Late Paleozoic shared dominance of the land flora with ferns, lycophytes, and sphenopsids. Since the beginning of the Mesozoic, however, most trees and forests have consisted of seed plants.

2. The oldest known seed plant is Elkinsia polymorpha, a "seed fern" from Late Devonian (Famennian) of West Virginia. Though the fossils consist only of small seed-bearing shoots, these fragments are quite well-preserved. This has allowed us to learn details about the evolutionary development of the seed. Another such fossil from about this time is Archaeosperma, also known only from fragments. At right is a diagram (modified from Stewart & Rothwell, 1993) of Archaeosperma arnoldii, showing four ovules surrounded by claw-like appendages.
The earliest seed plants produced their seeds along their branches without specialized structures, such as cones or flowers, unlike most living seed plants. The seeds were produced singly or in pairs, and were surrounded by a loose cupule. This small cup-like structure was lobed in the earliest seeds, producing a somewhat sheltered chamber at one end of the seed. Within this cupule, the seed was enclosed by a more tighly appressed tissue called the integument. The integument is a layer of tissue found in all seeds; it is produced by the parent plant, and develops into the seed coat. As the integument evolved to enclose the seed more tightly, an opening was left at one end, called the micropyle, which permitted pollen to enter and provide sperm to fertilize the egg cell. Both the integuments and cupule are believed to be the result of reduced and fused branches or leaves.

3. In later seed plants, a small pollen chamber appears just inside the micropyle. In modern cycads and conifers, this chamber exudes sticky fluids to aid in pollen capture, and as the fluid dries, it pulls the pollen inside the micropyle. This structure is preserved in detail in a number of recently discovered permineralized Devonian seeds. Besides preserving the pollen drop, minerals replaced the original tissues gradually, such that fine detail of the cell walls can be studied -- a few Permian seeds even have preserved embryos. Below you can see several Trigonocarpus from the Carboniferous.
By the end of the Devonian, a variety of early seed plants collectively known as "lyginopterids" appeared. These include Sphenopteris, a plant with fern-like leaves, but which bore seeds and cupules. You can see a picture of these leaves below. It is not clear whether Sphenopteris is a single group of closely related plants, or several with similar leaves.
Fossil Seeds: These are the permineralized seeds of a medullosan seed fern; such permineralized seeds are classified in the form genus Trigonocarpus. These particular fossils come from the Francis Creek Shale in Illinois, and are more than 300 million years old

4. The Carboniferous saw an increase in the number and kinds of seed plants. In the coal swamps of North America grew pteridosperms like Medullosa, a seed plant that resembles modern tree-ferns, but which bore seeds. Cordaites also grew in these swamps, and in a number of other habitats including ocean-edge environments similar to that of the modern mangrove. However, the cordaites are believed to be closer relatives of modern conifers. Both the medullosans and cordaites were small trees when compared to the great scale-trees which dominated these Late Paleozoic coal swamps. Seed plants were thus overshadowed in their early evolution by plants which did not produce seeds.
By the Westphalian (Late Carboniferous), the Voltziales first show up. These are believed to be the closest relatives of modern conifers, and in fact some paleobotanists classify them as conifers. By the Permian, the seed plants were beginning to produce large trees, and by the Triassic, all major groups of seedplants had appeared, except for the flowering plants.

5. The seed contains and disperses the embryo.
Below you can see a diagram showing the various parts of a typical seed. The seed includes three primary regions: the embryo, nutritive tissue, and seed coat. The embryo is the young sporophyte plant. This is what will grow into the new tree, shrub, vine, etc. The embryo is usually surrounded by some sort of nutritive tissue which will feed it during its early growth, until it can establish its own root system and leaves to support itself. The origin of this nutritive tissue varies from group to group of seed plants. Nutrients in the tissue are absorbed into the developing embryo by specially modified leaves called cotyledons. In some plants, the cotyledons may absorb all the nutrients before the seed is even dispersed, storing the food inside themselves.
Around the whole seed is a layer called the seed coat. This layer may be thick or thin, depending on the species, but it often contains light-sensitive chemicals. When conditions are right -- there is appropriate light and water -- the seed coat may trigger the germination of the seed. Many plants use this to break a period of dormancy, when the embryo remains inactive. This dormancy can be very important for plants in seasonal habitats, or any environment where the water or light vary greatly over time.

6. The seed does not develop from just any part of the plant, but from special structures called ovules. The ovule is an immature seed, which does not yet contain a viable embryo. It is only when the egg cell inside the ovule is fertilized by sperm that the ovule is called a seed. The ovule is surrounded by integument tissues which produce the seed coat, and in the earliest seed plants another layer called the cupule enclosed the entire ovule / seed.

7. Gymnosperm means ‘Naked seed’
Gymnosperm means ‘Naked seed’. However, when you look at a pine-cone you cannot actually
see any naked seeds, so what does this term imply ? The seeds are technically naked, because
pollen must land on the micropyle of the ovule, the micropyle exudes a drop of fluid, the
pollination droplet in most Gymnosperms. – in flowering plants (Angiosperm means ‘hidden
seed’) the pollen lands on a stigma, grows a pollen-tube down a style and then meets the ovule.
The term Conifer must also be understood to simply mean a cone-bearing plant – and it can
likewise be difficult to see how the fruit of a Podocarp, Ephedra, Ginkgo or Yew (each with a
single seed) can be called a cone – but it is! The Cones of pines, firs, spruces, and cycads on the
other hand are self evident.
Gametophyte generation wholly enclosed by Sporophyte generation: does not exist
independently. Megasporangia is contained in an ‘Ovule’ (An ovule comprises 2 layers
[integuments] surrounding a nucellus [merely a name for the mass of tissue] in which the spore
grows into the embryo sac [=Megasporangia or Female gametophyte]). After fertilisation, the
Embryo develops within an endosperm (haploid in Gymnosperms), and this in turn is enclosed
within a seed.
Gymnosperms are the most primitive of the seed plants. A seed comprises two parts: an
endosperm, which nourishes the embryo, and the embryo itself, which is fed by the endosperm.
In gymnosperms the endosperm grows from a spore (a cell with half the number of chromosomes
– n). Pollination may occur when the cone is small, but the endosperm continues to grow to
completion before fertilisation occurs. When fully grown the endosperm develops archegonia in
which single large nuclei act as egg cells. Only now does fertilisation occur, sometimes 12
months or more after pollination.
Flowering plants have made several important evolutionary advances over gymnosperms, which
is part of the reason there are 350,000 of them and just 900 gymnosperms. The flower is the
most obvious: It is bisexual, with a carpel & stigma; unlike a gymnosperm, the endosperm and
embryo develop in parallel by double fertilisation. The leaves are larger, broad and deciduous,
reflecting an improved water supply, which is due to the evolution of vessels – xylem elements
that are about 30 times the diameter of tracheids and 100 times as long.

14. Evolution of Cycads, Gymnosperms and Ferns

15. Div: Progymnospermophyta
Gymnosperm anatomy - secondary xylem tracheids, circular bordered pits - and fern-like fronds & reproductive dispersal by spores. (no seeds)
Arose in Upper Devonian 350 mya --> Pennsylvanian 290 mya
All extinct
Probably the immediate ancestor of all seed plants.
Archaeopteris

16. Div: Pteridospermophyta “Seed Ferns”
Gymnosperm anatomy and gymnosperm seed type with fern-like fronds. (seeds on fronds)
Arose during Carboniferous Period 345 mya --> Permian 250 mya.
All extinct
Probably the immediate ancestor of the cycads.

17. Div: Pteridospermophyta “Seed Ferns”
Ovules (megasporangium with embryo after fertilization) develop into “seeds” covered with two cells layers from integument or seed coat.
Naked Seed, “Gymnosperm”
Monoecious

18. Div: Cycadophyta “Cycads”
Resemble “palm trees”.
Cycad foliage does not bear ovules or seeds - these are in special seed cones (strobili); pollen (with sperms) produced in pollen cones.
Arose during Permian Period 280 mya --> extant
A dominant form of vegetation during the Jurassic and Triassic Periods --> 135 mya.

19. Div: Cycadophyta “Cycads”
All are dioecious: Micro and Megasporangia (strobili) on separate plants.
Cycas

21. Facts:
Extremely ancient (280 million years ago), coexisted with dinosaurs
Seed Plant
Characterized by a large crown of compound leaves and a stout trunk
Evergreen gymnosperms: plants that have seeds, but no flowers
NOT palms or ferns because: cycads have naked seeds born in cones, while palms are flowering plants whose seeds develop in fruits

22. More Facts: Dioecious: separate male and female plants
Male plants produce large cones
Cycads are long-lived, slow-growing, and have a low reproductive rate.
Found in subtropical and tropical parts of the world, can grow in semi-desert climates, in the sand, or even on rock, can thrive in either the sun or shade, and grow in small localized populations

23. Fun Facts:
Their roots contain cyanobacteria that exists in a symbiotic relationship (benefit both organisms) with the plant, and provide it with further nutrients by converting atmospheric nitrogen into a usable form
Only one species of cycad, Zamia pumila, has a range that extends into the United States. The distribution of this species includes southeastern parts of Georgia and southern parts of Florida where it is currently endangered.
Seminole Indians of the southeastern United States made use of the starchy matter in the stems of the cycad as an ingredient in bread. Although, most cycads contain toxic compounds within their tissues and seeds.
The roots of the cycad are retractable for protection against drought and fire

24. Fun Facts Continued… FEMALE CONES MALE CONES
There is some indication that the regular consumption of starch derived from cycads is a factor in the development of Lytico-Bodig disease, which is a neurological disorder with symptoms similar to those of Parkinson’s disease
Cycads were long thought to be pollinated by the wind. It has been shown, however, that beetles and small bees are important pollinators of these plants. Some cycads produce heat or odors to attract these insects.
FEMALE CONES
MALE CONES

25. Div: Cycadophyta “Cycads”
Reproductive cycle in cycads wind pollination; pollen droplet
4 - 6 months between
pollination &
fertilization
interval between pollination and fertilization: months.

26. Div: Cycadophyta “Cycads”
Two motile sperms produced by each pollen tube --> archegonial chamber.
Cycads & Ginkgos are
only seed plants with
motile sperm

27. Div: Cycadophyta “Cycads”
No fixed period of dormancy in cycads.

28. Evolution of Seed Plants
Derived Trait

29. Evolution of Seed Plants Gymnosperms
Pollen - Encased male microgametophyte (n) that produces
sperms (n).
(Frees plant from the need for water in the pollination
process.)
prothallus cell(s), tube cell(s), generative cell
---> sperms
Ovule - The female megagametophyte (n) with eggs (n) surrounded
by the old megasporangium (2n) with two layers from the
old sporophyte (2n) that will form the integument (2n).
(Frees plant from the need for water in fertilization.)
Cones - An axis bearing a tight cluster of scales or leaves for
reproduction. Scales either bear microsporangia or
meagasporangia in separate cones. (Pollen & Seed Cones)
Seed - ?

30. Evolution of Seed Plants Gymnosperms
Seed - The matured ovule with an embryo in a resting state.
Integument - (2n) May be fleshy
Female Gametophyte - (n) nuritive; includes nucellus
Embryo - (2n) forms from zygote after fertilization.

31. Evolution of Seed Plants Gymnosperms

32. Div: Ginkgophyta “Ginkgos, Maidenhair Trees, Yin hing (silver apricot)”
Arose during the Permian 250 mya.
Richly branched woody plant with simple leaves.
Ginkgo biloba living fossil

33. Div: Ginkgophyta 1. Large stems; small simple leaves; deciduous.
2. Dioecious (female more shrubby)

34. Div: Ginkgophyta 1. Large stems; small simple leaves; deciduous.
2. Dioecious (female more shrubby)
3. Has bud scales; dimorphism in branches. (long and spur shoots).
4. Stomates on abaxial (bottom) of leaf; two vascular bundles and 2 leaf traces per leaf.

35. Div: Ginkgophyta 1. Large stems; small simple leaves; deciduous.
2. Dioecious (female more shrubby)
3. Has bud scales; dimorphism in branches. (long and spur shoots).
4. Stomates on abaxial (bottom) of leaf; two vascular bundles and 2 leaf traces per leaf.
5. Initiation of cambium after primary growth; growth rings.
6. Cork cambium or phellogen develops in outer cortex --> phellem (cork cells, bark)

36. Div: Ginkgophyta Reproduction: Dioecious
Microsporangia (2n) - strobili
1 yr. --> microsporocyte (2n) > meiosis --> microspores (n) Spring --> pollen (male gametophyte)
Pollination (pollen droplet mucilaginous) -->
Megasporangia - ovules
1 yr. Development of megasporocyte (2n) --> meiosis --> megaspore (n) --> female gametophyte ( with egg - n) as pollen tube grows - after 5 mos.
(Aug-Oct) fertilization - development of seed - 2nd yr.

37. Div: Ginkgophyta Reproduction: Fertilization the 2nd Year
generative cell --> 2 flagellated sperms (just prior to fertilization) --> swim to end of pollen tube
egg from archegonium swells and forces apart neck cells --> exposed to pollen tube and sperm for fertilization.
Micropyle

38. Div: Ginkgophyta Reproduction: Development
seed

39. Div: Ginkgophyta Reproduction: Development
Outer fleshy layer of the integument emits foul order!
However, inner part of the seed is edible!

40. Div: Coniferophyta “Pines”, “Spruces” and “Firs”
Evolved during the Carboniferous Period 325 mya

41. Div: Coniferophyta “Pines, Spruces and Firs”

42. Div: Coniferophyta “Pines, Spruces and Firs”

43. Div: Coniferophyta “Pines”, “Spruces” and “Firs”
Evolved during the Carboniferous Period 325 mya
1. Leaves simple; often needle-like or scale-like.
2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
3. Pith and cortex restricted - xylem composes most of the stem.

44. Div: Coniferophyta “Pines”, “Spruces” and “Firs”
1. Leaves simple; often needle-like or scale-like.
2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
3. Pith and cortex restricted - xylem composes most of the stem.

45. Div: Coniferophyta “Pines”, “Spruces” and “Firs”
1. Leaves simple; often needle-like or scale-like.
2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
3. Pith and cortex restricted - xylem composes most of the stem.
4. Stem may be differentiated into long and spur shoots.

46. Div: Coniferophyta “Pines”, “Spruces” and “Firs”

47. Div: Coniferophyta “Pines”, “Spruces” and “Firs”
1. Leaves simple; often needle-like or scale-like.
2. Xylem compact, composed mostly of tracheids (seasonal growth - rings).
3. Pith and cortex restricted - xylem composes most of the stem.
4. Stem may be differentiated into long and spur shoots.
5. Leaf traces one or few per leaf.
6. Typically evergreen; loose leaves gradually.
7. Protostelic taproot.

48. Div: Coniferophyta “Pines”, “Spruces” and “Firs”

49. Div: Coniferophyta
Seed or Ovulate Cone
Pollen or Staminate Cone

50. Div: Coniferophyta
Pine Pollen

51. Div: Coniferophyta
Ovulate Pine Cones:

52. Div: Coniferophyta
Mature Pine Ovule with Two Archegonia:

53. Div: Coniferophyta
Ovules at Fertilization and with Embryo:

54. Div: Coniferophyta
Pine Seedling:

55. Div: Coniferophyta