Monocots begin their lives nourished by a single seed leaf (cotyledon). The leaf provides nutrients to the developing seed until it grows its first true leaves that can photosynthesize to make food. The true leaves are larger with parallel veins running from stem to tip. Monocots are herbaceous plants that typically don't grow large, but they are economically significant. Grasses are monocots that dominate grassland ecosystems such as prairies, and they are the source of grains such as rice, wheat, and corn that provide most of the world's food. Some monocots grow into trees sturdy enough to supply building materials, such as bamboo and palms. Many important tropical fruits, including bananas, coconuts, and pineapples, are from monocots. Some monocots in seasonal climates have evolved underground food storage organs such as bulbs to survive cold or dry conditions. The first flowers to bloom in the spring, such as daffodils and crocuses, are monocots from bulbs or bulb-like corms. Orchids are the most diverse group of monocots with over 22,000 species that are known for their beautiful flowers and relationships with insect pollinators.