Hydrilla bud. Light micrograph of a longitudinal section through an axillary bud on a Hydrilla plant, showing its internal structure. Hydrilla is a genus of aquatic plant native to the warmer parts of Asia and adapted to life in submerged freshwater environments. Seen here is a bud, an undeveloped embryonic shoot, with the apical meristem, or growing tip, at centre right (red). This is undifferentiated meristemic tissue, which lays down a growing root or shoot behind itself, pushing itself forward. Behind this (to the left) are leaf primordia (young leaves), which have recently formed.