(a) A protonema forms the earliest stage of a bryophyte life cycle. It is a thread-like chain of cells. Protonema is formed just after the germination of spores. It subsequently develops into a leafy gametophyte.
(b) An antheridium is the male sex organ of a plant. It produces the male gametes. It is present in the gametophyte phase of lower plants, but is present in the sporophyte phase of higher plants.
(c) Archegonium is a structure which is present in the gametophyte phase of some plants. The archegonium produces the female gamete.
(d) In this case, the diploid sporophyte is the dominant photosynthetic phase of the plant. The gametophyte is represented by the single to few-celled haploid gametophyte. Gymnosperms and angiosperms show this pattern.
(e) A leaf or cluste of leaves which bears sporangia is called sporophyll. Sporophylls can produce microspores or megaspores as the case may be.
(f) In this case, the gametes are similar in size, e.g. Spirogyra. The gametes can be flagellated or non-flagellated.
