The Fagaceae are monoecious trees and shrubs comprising 6-8 genera and about 800 species. The leaves are alternate and simple; the stipules are deciduous. The male flowers have a 4-7 lobed perianth of tepals and 4-40 stamens and are usually grouped in pendulous catkins. The female flowers are solitary or in small clusters. They have a 4-6 lobed perianth of tepals, and are often subtended by a series of bracteoles comprising an involucre. The single compound pistil of 3-6 carpels has an inferior ovary with 3-6 locules and two basal or nearly basal ovules in each locule. The fruit is called an acorn. It is a 1-seeded nut that is basally enveloped by a cupule derived from the involucre.

Each "thumbnail" image below is linked to a larger photograph.

Castanea dentata, American chestnut.  Saplings grown in Hawaii as an experiment to create a blight-free population on Hualalai.
Castanea mollissima and C. sativa, Chinese and Spanish chestnuts.
Castanea mollissima, Chinese chestnut, male flowers.
Quercus lobata, oak. The photo at right shows a nearly mature acorn with its involucral cup.
Quercus suber, cork oak.
Quercus sp. oak. Small brownish stipules are visible on the new growth at the upper right of the first photo. Note the pendulous catkins with many small male flowers (shown in greater detail in the second photo). A cluster of 3 female flowers is visible in the photo on the right. Note the series of pinkish bracteoles comprising an involucre that hides the lower portion of each ovary. Just below the 3-branched style, at the top of each green ovary, tiny pinkish perianth segments are visible.
Quercus sp. oak. Compare the two female flowers just past anthesis on the left with the two much more developed ones on the right. Not the enlargement of the ovary and the persistence and enlargement of the involucre.
Quercus sp., Zion, Utah.

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