This family is fairly herbaceous and has 700 species in 45 genera (Carr). This family is well known in northern climates because of its sharp hollow hairs that contain toxins. An interesting note about this family is that poisonous hairs are not found in all species. For example, Hawaii, due to its isolation and lack of large herbivores, has several species that have lost the stinging hairs. Mamaki (Pipturus albidus) is one example. It is used in Hawaii to make a tea just like other nettles are but lacks the toxic appendages. Hesperecride sandwicensis, however, is a native to Hawaii that has not lost the hairs, so this trait is not something found with "every" island species.
Systematics: Urticacids are monoecious plants with unisexual flowers. The stamen are in equal number to the tepals. Usually there are 4 of both. The gynoecium is monocarpus, with one pistil and one ovule and only one brush-like stigma. This is an important differentiation from the Moraceae family.
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