Corresponding with these five families, the sporangia or spore cases of ferns have five quite distinct forms on which the families are founded.
Fig. 1-4: Sporangia of the Five Families]
1. The Fern Family proper (Polypodiàceæ) has the spore cases stalked and bound by a vertical, elastic ring (Fig. 1). The clusters of fruit-dots containing the spore cases may be open and naked as in polypody (Fig. 2), or covered by an indusium, as in the shield ferns (Fig. 3).
2. The Royal Fern Family (Osmunda) has the spore cases stalked with only a rudimentary ring on one side, which opens longitudinally (Fig. 4).
3. The Climbing Fern Family (Lygodium, Schizæa) has the spore cases sessile in rows; they are small, nut-like bodies with the elastic ring around the upper portion (Fig. 5).[1]
[Footnote 1: These figures are enlarged.]
4. The Adder's Tongue Family (Ophioglóssum, Botrýchium) has simple spore cases without a ring, and discharges its spores through a transverse slit (Fig. 6).
5. The Filmy Fern Family (Trichómanes) has the spore cases along a bristle-like receptacle and surrounded by an urn-shaped, slightly two-lipped involucre; ring transverse and opening vertically (Fig. 7).
