The ontogeny of staminate and pistillate structures of white oak (Quercus alba L.) was established using light and scanning electron microscopy. It was found that staminate inflorescences were initiated in late spring. Individual staminate flowers were formed on the inflorescence axis in late June or early July and were structurally mature before the onset of dormancy in October. The staminate structures resumed development in mid-March and the inflorescences emerged from the bud as catkins in early April. Pistillate inflorescences were initiated in late summer and developed very little before dormancy. They were difficult to differentiate from lateral bud primordia during their early development. The inflorescences expanded rapidly and produced individual pistillate flowers during late March and early April. The pistillate flowers completed virtually all of their development during the 3 weeks prior to anthesis.
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