The Plants That Have No Flowers, No Seeds and No Roots

Yes — the algae growing green on a wet wall have none of the three. They have no true root, stem or leaf, produce no flower and never form a seed, yet they are plants.

Those gaps are exactly what classification uses to sort the plant kingdom. This page covers everything in the ICSE Class 7 Biology chapter on plant classification: the basis of classification, cryptogams and phanerogams, the three cryptogam groups, and the seed plants.

Because there are far too many kinds to study one at a time. Classification is the arrangement of living things into groups based on shared characteristics, so that studying one member tells you much about the rest.

It makes the study of plants systematic, shows the relationships between groups, and makes identifying an unknown plant possible.

The plant kingdom is divided on three main criteria:

- Body organisation — whether the body is a simple undifferentiated thallus, or is differentiated into true root, stem and leaf.
- Presence of vascular tissue — whether the plant has xylem and phloem to conduct water and food.
- Method of reproduction — whether it reproduces by spores or by seeds, and if by seeds, whether those seeds are enclosed.

A visit to any garden shows the extremes side by side: moss on a damp brick wall, ferns in a shaded pot, and a mango tree with flowers and seeds.

The criterion that does the most work is the last one, because reproduction is the most fundamental difference. Two plants can look quite similar and still belong to different groups if one makes spores and the other makes seeds.

Cryptogams are plants with hidden or no reproductive organs — they bear no flowers and no seeds, and reproduce by spores. Phanerogams have visible reproductive organs and reproduce by seeds.

Cryptogams include Thallophyta, Bryophyta and Pteridophyta. Phanerogams include the gymnosperms and the angiosperms.

The second distinction concerns the body itself. A thallus is a simple plant body not differentiated into true root, stem and leaf — it is often flat, ribbon-like or filamentous, as in algae and liverworts. A differentiated body has genuine roots, stems and leaves, each with its own tissues and job.

So the green film on a monsoon-damp wall is a thallus, while the tulsi plant in a courtyard has a fully differentiated body.

The case that needs care is Bryophyta, the mosses. They have structures that look like tiny stems and leaves, but these are not true ones — they lack vascular tissue, so they are called root-like, stem-like and leaf-like rather than roots, stems and leaves. That is why mosses count as an intermediate group between the thallus plants and the true vascular plants.

These are the three groups of cryptogams, and each is a step more advanced than the last.

Thallophyta — the simplest. The body is a thallus with no true root, stem or leaf, and there is no vascular tissue. It includes:

- Algae — green and autotrophic, containing chlorophyll, mostly aquatic. Examples: Spirogyra, Ulothrix, Chlamydomonas.
- Fungi — non-green and heterotrophic, with no chlorophyll, living as saprophytes or parasites. Examples: mushroom, Rhizopus (bread mould), yeast.

Bryophyta — the amphibians of the plant kingdom, because they live on land but need water for reproduction. The body is thallus-like or has stem-like and leaf-like parts, with rhizoids instead of true roots, and no vascular tissue. They are small and grow in damp, shady places. Examples: Funaria (moss), Marchantia (liverwort).

Pteridophyta — the first plants with true roots, stems and leaves and with vascular tissue (xylem and phloem). Still no flowers or seeds; they reproduce by spores borne on the underside of leaves. Examples: fern (Dryopteris), Marsilea, horsetail.

Bread going mouldy in a humid Indian kitchen is Rhizopus, and the ferns sold in nurseries for shaded balconies are pteridophytes.

Fungi are the group most often misplaced. They sit in Thallophyta but are not green and cannot photosynthesise — they absorb ready-made food, which is why a mushroom grows happily in the dark.

Phanerogams divide first by whether the seed is covered, then by the number of cotyledons.

Gymnosperms — the name means naked seeds. They bear no flowers, and the seeds are not enclosed in a fruit; they sit exposed on the surface of cones. They are mostly evergreen trees with needle-like leaves. Examples: pine, Cycas, deodar.

Angiosperms — the name means covered seeds. They bear flowers, and the seeds are enclosed inside a fruit formed from the ovary. They are the largest group of plants. Examples: mango, rose, wheat.

Angiosperms then split in two:

Monocotyledons — seed has one cotyledon, leaves have parallel venation, and the root system is fibrous. Examples: maize, wheat, rice, grass, coconut, banana.

Dicotyledons — seed has two cotyledons, leaves have reticulate (net-like) venation, and the root system has a taproot. Examples: gram, pea, mango, neem, sunflower.

Any Indian kitchen shows both: a grain of wheat is a monocot with one cotyledon, while a soaked gram seed splits neatly into two halves — its two cotyledons.

That splitting test is the most reliable one available without a microscope. A seed that separates into two equal halves is a dicot; one that cannot be split that way is a monocot — and the leaf venation of the same plant will confirm it.