Dichotomous Key/Dioon

Key to the species of Dioon:

Dioon

 * DIO1: Leaflets straight
 * DIO2: Leaflets curved or hooked

DIO1

 * DIO3: Leaflets less than fifteen millimeters wide.
 * DIO4: Leaflets over fifteen millimeters wide.

DIO2

 * Dioon sonorense: Leaflets less than five millimeters wide.
 * Dioon tomasellii: Leaflets over five millimeters wide.

DIO3

 * Dioon edule: Leaflet edges entire.
 * DIO5: Leaflet edges with spines

DIO4

 * Dioon rzedowskii: Petiole without spines.
 * DIO6: Spines present on petiole.

DIO5

 * DIO7: Leaflets inserted at 90 degrees to rachis.
 * DIO8: Leaflets inserted at 45 degrees or less to rachis.

DIO6

 * Dioon mejiae: Leaflet edges entire.
 * Dioon spinulosum: Leaflet edges with spines.

DIO7

 * Dioon holmgrenii: Leaflets seven to nine millimeters wide; Leaflets do not overlap.
 * Dioon merolae: Leaflets en to twelve millimeters wide; Leaflets overlap.

DIO8

 * Dioon caputoi: Leaflets less than five millimeters wide; Leaflets flat and do not overlap.
 * DIO9: Leaflets over five millimeters wide; Leaflets keeled and overlap.

DIO9

 * Dioon califanoi: Leaflets seven to eight millimeters wide.
 * Dioon purpusii: Leaflets eight to ten millimeters wide.