Q.Male and female gametophytes do not have independent, free-living existence in

When we look at the enormous variety of plants around us — pond scum, mosses on a damp wall, ferns in a shady corner, pine trees, mango trees — it helps to sort them into a few big families that share a way of life. This sorting is what plant classification is about, and the plant kingdom is arranged into five great groups: the algae, the bryophytes, the pteridophytes, the gymnosperms and the angiosperms.

The beauty of this order is that it is not random. Read from first to last, the five groups tell a story of plants gradually moving out of the water, building more complex bodies, developing better plumbing to move water and food, and slowly cutting their dependence on water for reproduction.

• Algae are the simplest — chlorophyll-bearing, food-making organisms with a plain thalloid body and no true roots, stems or leaves, living largely in water.
• Bryophytes, the mosses and liverworts, make the first move onto land but still need water to complete sexual reproduction, which is why they are called the amphibians of the plant kingdom.
• Pteridophytes, such as ferns and horsetails, are the first plants with true roots, stems and leaves served by vascular tissue — the xylem and phloem that conduct water and food.
• Gymnosperms are seed plants whose ovules and seeds lie naked, and whose pollen frees them from needing water for fertilisation.
• Angiosperms, the flowering plants, complete the trend: their ovules and pollen form inside flowers, and their seeds are enclosed within fruits. …