Which floating plant has a rosette of gray-green densely hairy leaves and a flower about 1/4 in across enclosed in a folded structure?

The correct answer is water lettuce. This floating plant is characterized by its distinctive rosette formation of leaves, which are gray-green in color and densely hairy. These features help to distinguish water lettuce from other aquatic plants. The folded structure that encloses the small flower, which is about 1/4 inch across, is also a key identifying trait.

Water lettuce thrives in warm, shallow waters and its unique leaf structure not only contributes to its ability to float but also plays a role in capturing sunlight for photosynthesis and providing habitat for various aquatic organisms. Its growth can sometimes lead to concerns regarding overpopulation, as it may block sunlight from reaching other plants beneath the water's surface.

In contrast, while water lilies and white waterlilies also have unique floating characteristics, their leaves and flowers differ significantly in size and structure, making them easily distinguishable from water lettuce. Giant duckweed, on the other hand, has a very small leaf size and does not exhibit the rosette formation or hairy leaf characteristics that are specific to water lettuce.