The Amaranthaceae are mostly herbs but rarely also shrubs or small trees comprising 169 genera and 2360 species further characterized by the presence of betalains and p-plastids. The leaves are alternate or opposite, simple, estipulate, and generally entire. The flowers are bisexual or unisexual, typically very small and tightly clustered, actinomorphic, frequently prickly due to bristly perianth and bracts, or the floral parts fleshy. Each flower is often subtended by a bract and two bractlets that commonly are scarious or membranous. A minute uniseriate perianth of 3-5, distinct or partially connate, fleshy, membranous, or papery sepals is also present. The androecium consists of usually 3-5 stamens that are opposite the sepals and which are distinct or united for part or all of their length into a membranous tube or crown-like structure, sometimes with minute appendages between the anthers. The compound pistil of 2-3 carpels has 1-3 styles and a superior ovary with one locule containing one or sometimes several basal ovules. The fruit is usually an achene, utricle, or circumscissile capsule.

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

Achyranthes splendens. This native Hawaiian shrub has greenish flowers, a common occurrence in the family. The bristly bracts and bractlets are shorter than the perianth segments in this species and are best seen associated with the unopened buds, although part of one is visible between the perianth segments on the left side of the open flower.
Alternanthera tenella, joy weed.
Amaranthus spinosus, spiny amaranth. This weedy species may be found in disturbed areas. It has tiny, greenish, prickly flowers typical of the family.
Celosia argentea, cockscomb. The larger pink appendages of the central open flower comprise the calyx. The pink-rimmed, white crown-like structure bearing anthers is the androecium. The pistil with its green ovary and pink style can be seen in the center of the flower. The bracts and bractlets, smaller than the flowers in this case, are best seen in association with the unopened flowers.
Charpentiera tomentosa, papala. Notice the tiny flowers with 5 exserted stamens in this Hawaiian native species.
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Gomphrena globosa, globe amaranth. The floral bracts and bractlets are colorful and showy and hide the perianth in this species. The staminal filaments form a column with pairs of appendages alternating with the anthers at the summit (visible most clearly in the third photo).  The third photo shows two flowers removed from the head, one with the bracts completely removed and the other (left) with the bracts separated to reveal the basally hairy, hyaline, reddish-tipped perianth segments.
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Nototrichium sandwicense, kulu'i. This native Hawaiian shrub has small, bristly flowers.
Chenopodium oahuense, 'aheahea. Hawaiian endemic, note the woody stem and tree-like habit that is unusual for the family. The flowers are tiny and greenish, and have a mealy, glandular surface. The infloresecences may contain a mixture of perfect and unisexual flowers.
Bassia hyssopifolia, five-horn smotherweed, Baker, OR, 2003.
Spinacia oleracea, spinach, female flowers.

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