In 1785, the pecan was described under the name _Juglans Pecan_, by Marshall in his Arboretum Americanum. In 1818, Thomas Nuttall, an English botanist, separated the hickories from the walnuts and butternuts, putting them under a new genus which he called _Carya_, naming the pecan _Carya olivaeformis_. Nuttall's classification was followed for many years until it was found that in the year previous to the publication of his work, 1817, C. S. Rafinesque, a French naturalist, had separated the hickories along the same lines as Nuttall and published them under the name _Hicoria_. In accordance with the laws of priority, Rafinesque's name, _Hicoria_, takes precedence over _Carya_. The family _Juglandaceæ_, embraces but two genera, _Juglans_ and _Hicoria_, the former including the walnuts and butternuts, and the latter the pecan and other hickories. With the exception of the Shellbark hickory, _Hicoria ovata_ Britton, and the Big shellbark, _Hicoria laciniosa_ Sargent, the pecan is the only one of the genus worthy of cultivation. _Family._ Juglandaceæ Lindl. Nat. Syst. Ed. 2, 180. 1836. Trees with alternate pinnate leaves and monoecious bracted flowers. Staminate flowers in long, drooping catkins, provided with three or more stamens and occasionally with an irregular-lobed perianth adnate to the bractlet and a rudimentary ovary. Anthers erect, with short filaments, two-celled; dehiscent longitudinally. Pistillate flowers bracted with a three to five, normally four-lobed calyx and sometimes with petals. Ovule solitary, erect, styles two, stigmatic along the inner surface. Fruit a bony nut, incompletely two to four-celled. Seed large, two to four-lobed, cotyledons corrugated, oily, without endosperm. _Genus._ Hicoria Raf. Med. Rep. (II) 5:352. 1808. Trees, with close or scaly bark, odd-pinnate leaves and serrate leaflets. Staminate flowers in slender drooping catkins, borne in groups of three, occasionally on the new shoots, but usually from buds just back of the terminal buds on last year's shoots, calyx naked, adherent to the bract, unequally two-third lobed or cleft; stamens with short filaments, three to ten in number. Pistillate flowers, two to eight, produced on a terminal peduncle, calyx four-parted, petals none, styles two to four, short, papillose. Fruit oblong, or obovoid, the husk separating into four parts; nut smooth or angled, bony, incompletely two to four-celled. Seed oily, sweet, edible or bitter and astringent. Natives of eastern North America and Mexico.