Aloe, Linnaeus, 1753

Grace, Olwen M., Klopper, Ronell R., Smith, Gideon F., Crouch, Neil R., Figueiredo, Estrela, Rønsted, Nina & Van Wyk, Abraham E., 2013, A revised generic classification for Aloe (Xanthorrhoeaceae subfam. Asphodeloideae), Phytotaxa 76 (1), pp. 7-14 : 8

Key to Aloe s. str. and its segregate genera

1. Dichotomously branched trees or large shrubs; leaves unspotted; dried leaves not persistent; flowers cylindrical to cylindric-ventricose, without a pronounced constriction above a bulbous basal swelling; perianth segments connate in lower half to almost free; mainly southern Africa, with an outlier species in Somalia........................................... 2

- Not dichotomously branched trees or large shrubs; leaves variously spotted to unspotted; dried leaves persistent or not; flowers variously shaped, with or without a pronounced constriction above a bulbous basal swelling; perianth segments variously connate to free; widespread in sub-Saharan Africa, Arabia, Madagascar and western Indian Ocean Islands .............................................................................................................................................................. 3

2. Leaves rosulate, apex tapering; inflorescence branched; southern Africa, with an outlier species in Somalia............. ................................................................................................................................................................... Aloidendron

- Leaves distichous, apex rounded; inflorescence simple (unbranched); Western Cape, South Africa (Cape Floristic Region ).............................................................................................................................................................. Kumara

3. Plants several-stemmed, shrubby or climbing; leaves spirally arranged, cauline dispersed, sheathing, separated by distinct internodes, unspotted; inflorescence usually simple; flowers cylindrical to slightly clavate or subventricose, sometimes slightly narrowed above the ovary, but without a pronounced constriction above a bulbous basal swelling; perianth segments ± connate; South Africa (mainly Western and Eastern Cape), with one species just entering Swaziland................................................................................................................................................... Aloiampelos

- Plants acaulescent or with simple or branched stems; leaves rosulate or distichous, seldom cauline dispersed, usually not separated by distinct internodes, variously spotted to unspotted; inflorescence variously branched or simple; flowers variously shaped, with or without a pronounced constriction above a bulbous basal swelling; perianth segments variously connate to almost free; widespread in sub-Saharan Africa, Arabia, Madagascar and western Indian Ocean Islands .......................................................................................................................................................... Aloe