| 1. Fruiting portion in the middle of the frond; two to four pairs of fertile pinnæ. Interrupted Fern. Osmunda Claytoniana. |
| 2. Fruiting portion at the apex of the frond. Sterile pinnæ palmate; rachis twining. Climbing Fern. Lygodium. |
| Sterile pinnæ pinnate; fronds large, fertile portion green, turning brown, forming a panicle at the top. Royal Fern. Osmunda regalis. |
| 3. Fruiting portion seemingly on a separate stock a few inches above the sterile. Sterile part an entire, ovate, green leaf near the middle; fertile part a spike. Adder's Tongue. Ophioglossum. |
| Sterile portion more or less divided; fruit in racemes or panicles, rarely in spikes. Grape Ferns. Moonwort. Botrychium. |
II
THOSE WHICH HAVE THE FRUITING PORTION ON THE BACK OR MARGIN OF FRONDS
A. INDUSIUM WANTING
| 1. Fruit-dots large, roundish; fronds evergreen. Rock species. Polypody. Polypodium. |
| 2. Fruit-dots small, roundish; fronds triangular. Beech Ferns. Phegopteris. |