| 1 | Plant | caulescent | 2 |
| | stemless | 5 |
| 2 | Peduncle | Visible and substantial | 3 |
| | Hardly visible and very short | 4 |
| 3 | Spike | complanate with distichous flowers | tortilis v. tortilis |
| | tubular with polystichous flowers, Leaves secund | curvifolia |
| 4 | Plant | open, Inflorescence mainly simple, Spike short and wide | lepidosepala |
| | dense rosette 15x 12cm wide. Inflorescence compound densely capitate | atroviridipetala var yagulensis |
| 5 | Plant | a dense flattened rosette | 6 |
| | a bulbose rosette | 14 |
| 6 | Leaves | evenly reflexed | 7 |
| | secund | 13 |
| 7 | Trichomes | feathery, Primary bracts longer than the spikes that are 1-3 flowered | plumosa |
| | not feathery | 8 |
| 8 | Peduncle | missing | 9 |
| | short | 11 |
| 9 | Spikes | mainly one flowered | atroviridpetala var atroviridipetala |
| | 4 – 12 flowered, to 5cm long | grandispica |
| 10 | Inflorescence | mainly with single spike | teloloapanensis |
| | with 2-6 spikes | 11 |
| 11 | Leaf Sheath | forming a bulb | atroviridipetala var. longepedunculata |
| | densely pressed together | mauryana |
| 12 | Inflorescence | to 7 spikes | 13 |
| | one spike | penascoensis |
| 13 | Floral Bracts & sepals | almost glabrous | boqueronensis |
| | dense lepidote | mauryana fa. secundifolia |
| 14 | Inflorescence | mainly simple distichous narrow lanceolate spike but sometimes with 1-2 smaller side spikes | ignesiae |
| | compound 3-7 spikes each to 7 flowered, leaves wavy after first 1cm, primary bracts shorter than spikes | caballoensis |
("Key to small Mexican Tillandsias (to 10-15cm diam) with green, greenish-yellow petals and included stamens.
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