Subject
- Specific Epithet: apiculata 1
- Specific Epithet: apiculatum 10
- Specific Epithet: apocarpa 5
- Specific Epithet: apocarpum 2
- Specific Epithet: argenteum 9
- Specific Epithet: asagrayana 1
- Specific Epithet: asperulum 1
- Specific Epithet: asplenioides 7
- Specific Epithet: asprella 17
- Specific Epithet: atrovirens 1
- Specific Epithet: attenuatus 18
- Specific Epithet: austini 1
- Specific Epithet: austinii 2
- Specific Epithet: autumnalis 2
- Specific Epithet: barbata 2
- Specific Epithet: barbula 1
- Specific Epithet: bicuspidata 1
- Specific Epithet: biddlecomiae 9
- Specific Epithet: bidentata 1
- Specific Epithet: blandowii 2