Diagnostic key for genera of Amaranthaceae s.str. occurring in Saudi Arabia

1. Leaves alternate..................................................................................................................................................................................2

2. Flowers unisexual...............................................................................................................................................................................3

3. Each fertile flower subtended by two modified sterile flowers...................................................... Digera muricata subsp. muricata

3. Fertile flower never subtended by modified sterile flowers............................................................................................. Amaranthus

2. Flowers hermaphrodite.......................................................................................................................................................................4

4. Fruit including one seed; stigma 1, capitate .......................................................................................................................................5

5. Annual herb; tepals 1.00− 1.25 mm long ......................................................................................................... Nothosaerva brachiata

5. Perennial herb; tepals 3.25−4.00 mm long................................................................................................................... Saltia papposa

4. Fruit including 2 or more seeds; stigmas 2−3, linear .............................................................................................................. Celosia

1. Leaves opposite ..................................................................................................................................................................................6

6. Synflorescence in axillary glomerules and/or terminal heads (no terminal spike- or panicle-structures) .........................................7

7. Stigma 1, capitate .......................................................................................................................................................... Alternanthera

7. Stigmas 2, linear .................................................................................................................................................. Gomphrena globosa

6. Synflorescence in terminal spike- or panicle-structures and/or terminal heads.................................................................................8

8. Sterile flowers present ......................................................................................................................... Pupalia lappacea var. velutina

8. Sterile flowers absent .........................................................................................................................................................................9

9. Synflorescence in terminal heads; pseudostaminoids absent ................................................................ Psilotrichum gnaphalobryum

9. Synflorescence in terminal spike-structures; pseudostaminoids present..........................................................................................10

10. Stigmas 2, linear ......................................................................................................................................................................... Aerva

10. Stigma 1, capitate .............................................................................................................................................................................11

11. Pseudostaminoids not fringed................................................................................................................ Psilotrichum gnaphalobryum

11. Pseudostaminoids fringed................................................................................................................................................. Achyranthes