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Gymnospermae (裸子植物)






Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

[Engler's syllabus (エングラー体系), Angiospermae (被子植物)]

Gymnospermae (Gr. gymnos = naked + Gr. sperma = seed) and the informal term "gymnosperm"

General characteristics

vegetable organ = vegetative type (or sporophyte) → remarkable, asexual
vegetable organ = gametophyte → degenerative, parasitical, sexual


sporophyte = primarily endoderm
gametophyte ⇒ ovule

macrophyll → macrosporogphyll (果葉) → macrosporangium ← n | 2n → ovule → macrospore
microphyll → microsporophyll (粉葉) → microsporangium ← n | 2n → anther cell or pollen sac → microspore

Life cycle
life cycle
Table. Comparison of characteristics between Cycadopsida and Coniferopsida
CycadopsidaConiferopsida
LeafLarge, complex, fern-frond-like compoundSimple, often scale-like or needle-like
Leaf traceNumerousOne to a few, simple
Leaf basePersistent, forming an "armor" on the stemNot persistent
StemNot differentiated into long and spur shootsHaving long and spur shoots
WoodPith and cortex extension, as compared with xylem and phloem. Xylem loosely arranged with broad parenchymatous rays (monoxylix)Pith and cortex restricted, xylem composing bulk of stem. Xylem compact, composed mostly of tracheids, rays narrow (pycnoxylic)
Ovule (+ seed)Ovlues borne singly on leaves, in simple strobili, on a megasporophyll (Cycas), or on an conical axis. Seed is radical symmetry.Ovlues often borne in compound strobili or ovlues borne singly. Seed is bilateral symmetry

I. Class Cycadopsida Brongn. ソテツ綱


1869 Hrase S (平瀬作五郎): discovered sperms from Ginkgo biloba
1869 Ikeno S (池野成一郎): discovered sperms from Cycas revoluta

→ kinship with Pteridophyta

Potonie (Cycadofilices ソテツシダ類): capsule (杯状体)_sulpynx
Mudullose: capsule – fusion with integument__________
Cycas: basicall same with Mudullose_________________shrinkage
Subclass Pteridospermidae (シダ状種子植物*)
Devonian- Jurassic
Subclass Cycadidae (ソテツ)
Cycas and confiers – development of microspore
cycas and conifer
(♀) free nuclear division → archegonium = same with Ginkgo
The maturation of seeds needs longer time

Ex. June ♀ macrospore cell → pollination / miosis: tissues developed one year later → fertilization in the next year

Order Bennettiales *: Triassic
Order Cycadales (ソテツ): Upper Triassic-present
Cycadaceae

Leaf emergence: curly in the early stage like Osmunda japonica

Zamiaceae
Nilssoniaceae *
Subclass Pentoxylidae*
One family and one order
Order Pentoxylales
Pentoxylaceae
→ phylogenetical reation is unknown, probably shrub
Subclass Ginkgopsida
Order Ginkgoales Trichopityaceae *
Lower Permian in France
Ginkgoaceae (イチョウ)
(♂)
cycas and conifer
(♀) free nuclear division → archegonium
Ginkgo biloba, one species in one genus in one family in the present

Fossile: 17 or more species → diverse (after Upper Paleozoic)

*: extinct (fossil records)

II. Class Coniferopsida 球果植物綱 (針葉樹綱)


Evolution of flower → one scale = one flower →
The whole of pine cone = inflorescence
Species non-producing cones in Coniferopsida

1. devolution → 1 seed (e.g., Podocarpus)
2. unknown: Taxus → many characteristics differ from the other coniferous species

→ Taxopsida (establishing independent version of class)
Fossil record: differentiated in the vicinity of the Permian

Araucariaceae → Pinaceae → Taxodiaceae → Cupressaceae

× Podocarpaceae forming epimatium → different phylogeny

Order Cordaitales*
upper Devonian - the Permian* (flourished in the Carboniferous)
Order Coniferales (球果植物目) = Pinales (マツ目)
Walchiaceae (Lebachiaceae)*
Voltziaceae*
Palissyaceae*
Araucariaceae (ナンヨウスギ)
Sciadopityaceae
Pinaceae (マツ, conifer)
Cupressaceae (ヒノキ): Actinostrobus Miq. (WA)
Order Taxales (イチイ)
Podocarpaceae マキ
Cephalotaxaceae イヌガヤ
Taxaceae イチイ

III. Class Gnetopsida (Chlamydospermopsida, グネツム綱)


Growth

Leaf = finite or determinate growth (exception: Lygodium japonicum, Diplopterygium glaucum – growth point on apex)
Stem = indeterminate growth (exception: Welwitschia – growth point on leaf base)
Vessel present + xylem fiber present
Companion cell developed in a few species (Gnetum) → close to Angiospermae
Lignin structure close to Angiospermae
Ovule (♀): enveloped by a structure like a perianth or floral envelope s.s., connate scales)
Microsporangium (♂): the number of microsporangia present in an androphore or a microsporangiophore are constant on each species

female flower connoted vestigial or immature ♂ – Welwitschia, Gentum

Order Ephedrales (= Ephedraceae)

(♂) The microsporangiate strobili have rounded apices, while those of the ovulate strobilis are acute. The strobili of E. antisyphilitica are already visible and well developed in the vicinity of abilene and elsewhere in texas, at the nodes among the fasciculate, photosynthetic axis (Bold et al. 1980).
ephedra
Ephedra (マオウ): 40 spp., xerophytic, 3-5 m in height
Ephedra
Fig. Ephedraceae. a: anther, c: column, i: integument, b: perianth (or outer integument), p: macrosporangium
Ephedra
Fig. Ephedra trifurca Torr. ex S. Wats.

Order Welwitschiales (= Welwitschiaceae)

Gnetum and Welwitchia
No stalk cell stage
Pollen formation of Welwitchia is earlier than that of Gnetum because the karyokinesis makes a time
Welwitschia Hook. f.
= W. mirabilis Hook. f. (= W. bainesii Hook. f. nom. inval.)

Order Gnetales (= Gnetaceae)

ca. 50 spp. Gnetum L. (G. gnemon, the type)
Distribution
Fig. Distribution of genus Gnetum
Gnetum
Fig. Gnetum gnemon L., Gnemon tree
♀ flower = female gametophyte = the structure is clearly Gymnospermae (archaegonium, not developed)
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