Let me share with you a difference between psilopsida and lycopsida.
| Aspect | Psilopsida | Lycopsida |
| Common name | Whisk Ferns | Clubmosses |
| Habitat | Found in tropical and subtropical regions, often in moist environments | Found in a variety of environments, including moist woodlands and arid areas |
| Vascular Tissues | Lack true leaves and roots | Have true leaves and roots; |
| Stem | simple dichotomously branching stems | Stems may be dichotomously or laterally branched |
| Leaves | Lack true leaves | Have microphylls (small leaves with a single unbranched vein |
| Rhizome | Dichotomously branching | Typically horizontal and underground |
| Strobilus | May have simple, unbranched strobili (reproductive structures) | Often have complex strobili with sporophylls arranged in whorls |
| Sporangia | Sporangia typically borne on the upper surface of the sporophyte | Sporangia borne on the lower surface of specialized sporophylls |
| Roots | Absent or reduced roots, with some species having rhizoids | True roots are present, that emerges from the rhizome |
| Homosporous or Heterosporous | Mostly homosporous (produce one type of spore) | Mostly homosporous, but some heterosporous species exist |
| Examples | · Psilotum · Tmesipteris |
· Lycopodium
· Selaginella · Isoetes |