Section A
Class I. Key to Gill-bearing Mushrooms (Agarics)
| 1. | Plants fleshy, soon decaying, | 2. |
| Plants leathery, woody, persistent, | 12. | |
| 2. | Juice milky, white, or colored, | Lactarius. |
| Juice watery, | 3. | |
| 3. | Stem central, or nearly so, | 4. |
| Stem lateral, eccentric or wanting, | 11. | |
| 4. | Spores white, | 5. |
| Spores rosy, pink or salmon color, | 15. | |
| Spores yellowish-brown, ochre color, | 17. | |
| Spores dark brown, | 21. | |
| Spores black, | 24. | |
| 5. | With volva and ring, | Amanita. |
| Volva and no ring, | Amanita (sub-genus Amanitopsis). | |
| Ring and no volva, | 6. | |
| No ring and no volva, | 7. | |
| 6. | Gills free, ring movable, pileus scaly, | Lepiota. |
| Gills adnate, pileus generally smooth, | Armillaria. | |
| 7. | Gills thin, edge acute, | 8. |
| Gills in the form of folds, obtuse edge, | 10. | |
| 8. | Gills decurrent or stem fleshy. | Clitocybe. |
| Gills sinuate, notched behind, stem fleshy, | Tricholoma. | |
| Gills adnate, not decurrent, stem cartilaginous, | Collybia. | |
| Stem fleshy, cap often bright color, | 9. | |
| 9. | Plants rigid, gills even, cap bright, | Russula. |
| Plants with waxy gills, | Hygrophorus. | |
| 10. | Gills decurrent, plant terrestrial, | Cantharellus. |
| 11. | Spores white, | Pleurotus. |
| Spores yellowish or brown, | Crepidotus. | |
| 12. | Gills serrated on their edges, stem central or lateral, | Lentinus. |
| Gills entire, stem central, | 13. | |
| Stem lateral or wanting, | 14. | |
| 13. | Gills simple, pileus dry, soon withering, then reviving when moist, | Marasmius. |
| 14. | Gills deeply splitting, with weak hairs, | Schizophyllum. |
| Gills united by veins, plant corky, | Lenzites. | |
| 15. | Volva, no ring, | Volvaria. |
| No volva, ring present, | Annularia. | |
| No volva, no ring, | 16. | |
| 16. | Gills free, rounded behind, cohering at first, | Pluteus. |
| Gills adnate or sinuate, stem fleshy, soft, waxy, cap fleshy, margin incurved, | Entoloma. | |
| Gills decurrent, stem fleshy, | Clitopilis. | |
| 17. | Ring continuous, pileus with scales, | Pholiota. |
| Ring cobwebby or evanescent, not apparent in old specimens, | 18. | |
| Ring wanting, | 19. | |
| Stem with cartilaginous rind, | 21. | |
| 18. | Gills adnate, plants on the ground, | Cortinarius. |
| 19. | Gills decurrent, stem fleshy, gills easily separating, | Paxillus. |
| Gills not decurrent, stem fleshy, | 20. | |
| 20. | Pileus fibrillose, or silky, | Inocybe. |
| Pileus smooth and sticky, | Hebeloma. | |
| 21. | Veil remaining attached to margin of pileus, often not seen in old specimens, | Hypholoma. |
| Veil on stem as a ring, | 22. | |
| Margin of cap incurved when young, | Naucoria. | |
| 22. | Gills separate on the stem, | Agaricus or Psalliota. |
| Gills united with stem, | Stropharia. | |
| Gills adnate or sinuate, | 23. | |
| 23. | Margin of pileus incurved when young, | Psilocybe. |
| Margin of pileus always straight, | Psathyra. | |
| 24. | Pileus of normal form, | 25. |
| 25. | Pileus fleshy, membranaceous or deliquescent, | 26. |
| 26. | Gills deliquescent—inky fluid, | Coprinus. |
| Gills not deliquescent—ring present, | Annellaria. | |
| Gills not decurrent—ring wanting, | 27. | |
| 27. | Pileus striate—plants small, | Psathyrella. |
| Pileus not striate, stem fleshy, margin exceeding the gills, | Panaeolus. |