1. Development of deep roots capable of penetrating the soil.
2. Development of water proofing material like cutin on leaves to reduce water loss.
3. Development of strong woody material to anchor and support above ground.

Industrial uses of algae:
1. Agar, a major medium for laboratory culture, is produced from algae.
2. Sea weeds are major source of fertilizers
3. Algae is used as bio-fuel
4. Algae is used for sewage treatment

Economic Importance of Moss:
1.Some mosses provide food for herbaceous mammals, birds and other animals.
2. Species of Sphagnum, a moss, provide peat that have long been used as fuel, and because of their capacity to hold water as packing material for transshipment of living material.
3. Mosses along with lichens are the first organisms to colonise rocks and hence, are of great ecological importance. They decompose rocks making the substrate suitable for the growth of higher plants.
4.Since mosses form dense mats on the soil, they reduce the impact of falling rain and prevent soil erosion.

1.Fibrous root system
2.Single cotyledon in seeds
3.Parallel venation in leaves
4.Trimerous flowers.

External features of dicotyledons:
1. Tap root system
2. Two cotyledons in seeds
3. Reticulate venation in leaves
4. Tetramerous or pentamerous flowers.

Differences between pinus and cycas

1. The main plant body is a sporophyte which is differentiated into true root, stem and leaves. These organs possess well-differentiated vascular tissues.
2. The leaves in pteridophyta are small (microphylls) as in Selaginella or large (macrophylls) as in ferns.
3. The sporophytes bear sporangia that are subtended by leaf-like appendages called sporophylls. In some cases sporophylls may form distinct compact structures called strobili or cones (Selaginella, Equisetum).

The disadvantage of the artificial system are given below
i) This system uses only a few superficial characters(i.e, habits, numbers, colors and shapes of leaves, etc) Which lead to many organisms grouped togeather.
ii)They considered mainly the vegetative characters or  the androecium characters as given by Linnaeus.cters i

The sporophytes bear sporangia that are subtended by leaf-like appendages called sporophylls. In some cases, sporophylls may form a distint compact structure called strobili or come. The sporangia produce spores by meiosis in spore mother cells.

Seed habit developed in extinct pteridosperm or Cycadofilicales. It is a group intermediate between cycads and ferns. The habit made the seed plant independent of the requirement of external source of water at the time of fertilizaton. in seedless vascular plants, the gametophyte must develop on moist soil with a thin sheet of water. The latter is required for the swimming of sperms for reaching the female sex organs.
As a result, seedless vascular plant could never become true land plants.They were popularly called as amphibian of plant kingdom

Ferns are widely distributed all over the world in warm, moist and shady places. The main plant body of ferns is sporophyte, which is differentiated into underground stem called rhizome, roots and aerial shoots with leaves. They may be homosporous (e.g., Dryopteris, etc) or heterosporous (e.g., Marsilea). Spores are born in the sporangia which are grouped in sori. Some common ferns are Dryopteris, Pteridium, Pteris, etc.

Mosses are widely distributed from the Arctic through the tropics to parts of Antarctica. The gametophytic plant body is with leafy axis and shows a radial symmetry. The rhizoid are multicellular, branched and have oblique septa. Sex organs, i.e., antheridia and archegonia are usually borne in groups at the apices of reproductive branches. The sporophyte is usually differentiated into foot, seta and capsule.

Red algae The photosynthetic pigments located in the chromatophores are chlorophyll-a, d and \(\alpha \), \(\beta \) -carotenes, xanthophyll and biliproteins.
Green algae   Chromoplasts contain chlorophyll-a, b, carotene and xanthophyll.
Brown algae The chromatophores contain chlorophyll-a, c and \(\beta \),  \(\alpha \)-carotnes and xanthophyll.

The characters used in natural system of classification are morphology, anatomy, reproduction, cell structure, behaviour and biochemistry. The similarity in large number of characters show kinship.
Examples 
(i) Monocotyledons have one cotyledon in their seeds and their leaves have parallel ventation.
(ii) Dicotyledons have two cotyledons in their seeds and their leaves have reticulate venation.