The primary means of reproduction and dispersal for Earth’s most successful plants is seeds, which develop from the female gametophyte and its associated tissues. Seed plants show the greatest evolutionary complexity in the plant kingdom and are the dominant plants in most terrestrial environments. Seeds are reproductively superior to spores for three main reasons. First, a seed contains a multicellular, well-developed young plant with embryonic root, stem, and leaves already formed, whereas a spore is a single cell. Second, a seed contains a food supply. After germination, the plant embryo is nourished by food stored in the seed until it becomes self- sufficient. Because a spore is a single cell, few food reserves exist for the plant that develops from a spore. Third, a seed is protected by a resistant seed coat. Like spores, seeds can live for extended periods of time at reduced rates of metabolism, germinating when conditions become favourable.