Flowering Plant Families, UH Botany

The Casuarinaceae are monoecious or dioecious trees and shrubs comprising one genus and about 50 species with green, jointed, whorled photosynthetic branchlets. The leaves are minute and whorled. The male flowers are minute and are clustered at the tips of branchlets in catkin-like strobili. Each flower consists of a single stamen, a subtending bract and 2 pairs of bracteoles. The female flowers are in ovoid clusters, each flower consists of a pistil, a subtending bract and two bracteoles. The bicarpellate pistil has two long, filiform stigmas from a short style. The ovary initially has two locules with two ovules in each but one locule is generally completely aborted at anthesis. The bracts and bractlets enclosing the ovaries persist and become woody, closely resembling a cone. Eventually, the bracts of individual flowers separate, releasing the 1-seeded samaroid fruits.

Casuarina equisetifolia, ironwood. Note the needle-like photosynthetic branchlets and green, conelike fruiting structures in the 2nd photo. Just below these on the center and right branches are about half a dozen tiny, reddish brown female inflorescences. An elongated, cream-colored immature male inflorescence can be seen at the tip of each of many of the branchlets on the left side of this photo. Whorls of tiny brown to pale yellow-green leaves may be seen at regular intervals along the stems in the closer views. The lower right photo (#7) shows two shoots with female inflorescences on the left and two shoots with male inflorescences on the right. Each female flower has a deeply 2-lobed red stigma. Each male flower consists of a single stamen with associated bracteoles.

Casuarina sp. Female inflorescence, note deeply 2-lobed stigmas.

Casuarina sp., ironwood. This photo shows a mature cone-like fruiting structure. The fruits have been released through the openings created by separation of the woody bracts and bracteoles.