NCERT grounding
NCERT Class 11 Biology, Chapter 3 (§3.3) introduces pteridophytes as the horsetails and ferns and states their defining evolutionary place precisely: they are the first terrestrial plants to possess vascular tissues — xylem and phloem. The text contrasts them with bryophytes, where the dominant phase is the gametophyte, by stressing that in pteridophytes the main plant body is a sporophyte differentiated into true root, stem and leaves. NIOS Biology (§3.3) reinforces the same point, classifying pteridophytes under Trachaeophyta because they contain conducting tissue.
"Evolutionarily, they are the first terrestrial plants to possess vascular tissues — xylem and phloem."
NCERT Class 11 Biology · §3.3 Pteridophytes
What makes a pteridophyte
A pteridophyte is recognised by a single architectural advance over the bryophytes: a conducting system. NCERT places this development at the heart of the group, calling them the first land plants to carry differentiated xylem and phloem. Xylem moves water and dissolved minerals upward from the soil; phloem distributes the food made in the leaves. With plumbing in place, the plant body could grow larger, stand erect against gravity and supply distant tissues — a freedom no alga or bryophyte enjoyed. This is why the group is also called the lower vascular plants or, in NIOS, members of Trachaeophyta.
The second feature follows from the first. Because the sporophyte now has a vascular supply, it can support genuine organs. NCERT records that the main plant body is a sporophyte differentiated into true root, stem and leaves — organs that bryophytes only mimic with root-like, stem-like and leaf-like structures. Pteridophytes are usually found in cool, damp, shady places, though some tolerate sandy soils; they are used as soil-binders, as medicinal plants and as ornamentals.
Three diagnostic features separate pteridophytes from the groups on either side of them in the chapter.
Vascular tissue
First land plants with xylem and phloem; absent in algae and bryophytes.
True organs
Sporophyte bears true root, stem and leaves — not merely root-like appendages.
Dominant sporophyte
The conspicuous diploid sporophyte is the main phase; the gametophyte is tiny.
The sporophyte body and its leaves
On the sporophyte, the leaves carry the spore-producing apparatus. NCERT distinguishes their size sharply: the leaves may be small — microphylls, as in Selaginella — or large — macrophylls, as in ferns. The sporophyte bears sporangia that are subtended by leaf-like appendages called sporophylls. In some genera the sporophylls cluster into distinct compact structures called strobili or cones, as in Selaginella and Equisetum. Inside the sporangia, spore mother cells divide by meiosis to produce haploid spores. NIOS adds the fern's surface detail: on the underside of fern leaves the sporangia occur in clusters called sori (singular sorus), which may be covered by a membrane, the indusium, while young fern leaves are circinately coiled.
Figure 1. The fern sporophyte: a horizontal rhizome bearing adventitious roots and large macrophyllous fronds. On the leaflet underside the sporangia occur in clusters called sori, where spore mother cells undergo meiosis.
Four classes of pteridophytes
NCERT classifies the pteridophytes into four classes, each with named examples. Memorising the class–genus pairing is the highest-yield factual task in this subtopic, because NEET routinely tests it through matching and "wrongly matched" formats.
Salvinia and Marsilea are aquatic ferns also studied with this group; NCERT names Salvinia alongside Selaginella as a key heterosporous genus. The four-class scheme and these scattered genera together cover almost every name NEET has ever lifted into a matching question on this topic.
Life cycle and the prothallus
The pteridophyte life cycle is the part NEET examiners return to most often, because every term in it is testable. The cycle begins with the dominant diploid sporophyte. Spore mother cells inside the sporangia — borne on sporophylls — undergo meiosis to make haploid spores. A spore germinates into a small, multicellular, free-living and mostly photosynthetic thalloid gametophyte called the prothallus. NCERT stresses that these gametophytes require cool, damp, shaded places; because of this restricted requirement, and the need for water at fertilisation, living pteridophytes are confined to narrow geographical regions.
The prothallus bears the sex organs: male antheridia and female archegonia. Water is required to carry the antherozoids — the motile male gametes released from the antheridia — to the mouth of the archegonium. Fusion of a male gamete with the egg in the archegonium forms the zygote, which grows into the multicellular, well-differentiated sporophyte — closing the loop and re-establishing the dominant phase.
The pteridophyte life cycle (haplo-diplontic)
-
1 · 2n
Sporophyte
Dominant diploid plant with true root, stem, leaves bearing sporophylls.
-
2 · 2n
Sporangia
Spore mother cells inside sporangia undergo meiosis.
meiosis -
3 · n
Spores
Haploid spores released; germinate in damp, shaded soil.
-
4 · n
Prothallus
Small free-living gametophyte bearing antheridia & archegonia.
-
5 · 2n
Zygote
Water carries antherozoids to egg; zygote grows into a new sporophyte.
water needed
Note where meiosis sits: it occurs in the spore mother cells of the sporophyte, producing spores — not at gamete formation. This is the answer to the recurring NCERT exercise asking where reduction division takes place in a fern. The gametophyte, by contrast, makes gametes by mitosis.
Homospory, heterospory and the seed habit
Most pteridophytes are homosporous: all their spores are of one similar kind. But a few genera — NCERT names Selaginella and Salvinia — produce two kinds of spores: large megaspores and small microspores. These are the heterosporous pteridophytes. The megaspores germinate into female gametophytes and the microspores into male gametophytes.
Homosporous
1
single spore type
- All spores similar in size and kind
- Gametophyte usually bisexual
- Examples: most ferns, Lycopodium, Equisetum, Psilotum
Heterosporous
2
megaspore + microspore
- Two spore types: large mega-, small micro-
- Female gametophyte retained on parent sporophyte
- Examples: Selaginella, Salvinia
The significance of heterospory is the single most quoted evolutionary point in the chapter. In these plants, NCERT records, the female gametophytes are retained on the parent sporophyte for variable periods, and the development of the zygote into a young embryo takes place within the female gametophyte. This protected, dependent development of the next generation on the parent plant is described as a precursor to the seed habit — an important step in evolution that anticipates the seed plants studied in the next section.
Heterosporous genera in NCERT
Selaginella and Salvinia are the only two pteridophyte genera NCERT names as heterosporous — and the retention of the female gametophyte on the parent is the recognised precursor to the seed habit.
Worked examples
Name the dominant generation of pteridophytes and state the ploidy of the cells that undergo meiosis in it.
The dominant generation is the sporophyte, which is diploid (2n). Meiosis occurs in the diploid spore mother cells inside the sporangia, producing haploid (n) spores. The gametophyte (prothallus) then forms gametes by mitosis, so no reduction division occurs at gamete formation.
From an evolutionary point of view, in which group is the retention of the female gametophyte with the developing young embryo on the parent sporophyte first observed?
Pteridophytes — specifically the heterosporous genera Selaginella and Salvinia. This retention of the female gametophyte, within which the zygote develops into a young embryo, is the precursor to the seed habit. It is observed before gymnosperms, so pteridophytes are the correct answer.
Match: (a) Microphyll (b) Strobilus-bearing horsetail (c) Pair of heterosporous pteridophytes (d) Spore clusters on fern leaf underside.
(a) Microphyll → Selaginella; (b) Strobilus-bearing horsetail → Equisetum; (c) Heterosporous pair → Selaginella and Salvinia; (d) Spore clusters → sori. NCERT names Selaginella for microphylls and both Selaginella and Equisetum for strobili/cones.