Fig. 5-7: Indusium
THE FERN FAMILY PROPER OR REAL FERNS
POLYPODIÀCEÆ
Green, leafy plants whose spores are borne in spore-cases (sporangia), which are collected in dots or clusters (fruit-dots or sori) on the back of the frond or form lines along the edge of its divisions. Sporangia surrounded by vertical, elastic rings bursting transversely and scattering the spores. Fruit-dots (sori) often covered, at least when young, by a membrane called the indusium. Spores brown.
[THE POLYPODIES]
1. POLYPODY. Polypodium
(From the Greek meaning many-footed, alluding to the branching rootstocks.)
Simple ferns with stipes articulated to the creeping rootstocks, which are covered with brown, chaffy scales. Fruit-dots round, naked, arranged on the back of the frond in one or more rows each side of the midrib. Sporangia pedicelled, provided with a vertical ring which bursts transversely. A large genus with about 350 species, widely distributed, mostly in tropical regions.
(1) COMMON POLYPODY. Polypodium vulgare
Fronds somewhat leathery in texture, evergreen, four to ten inches tall, smooth, oblong, and nearly pinnate. The large fruit-dots nearly midway between the midrib and the margin, but nearer the margin.