Fertile Pinnules Spread Open Cinnamon Fern.

Trichomanes Boschianum Fruiting Pinnules of Filmy Fern Crosiers Noted Fern Authors Spray of the Bulblet Bladder Fern

These divisions of the pinnæ are called pinnules.

When a frond is tripínnate the last complete divisions are called ultimate pinnules or segments.

Fruit in lines on the margin of the pinnules; under surface of the fronds covered with whitish powder.

[Illustration] 2. Indusium formed by the reflexed margin of the pinnules.

[Illustration] Indusium narrow, seldom continuous, formed by the margin of separate lobes or of the whole pinnules; often inconspicuous, fronds usually hairy.

[Illustration] Indusium of the reflexed edges, at first reaching to the midrib, or nearly so; later opening out nearly flat; fruiting pinnules pod-like; sterile fronds broad.

Fronds broadly triangular, ternate, one to three feet high or more, the widely spreading branches twice pinnate, the lower pinnules more or less pinnátifid.

pseudocaudàta has longer, narrower and more distant pinnules, and is a common southern form.

Adiantum Ferns with much divided leaves and short, marginal sori borne at the ends of free-forking veins, on the under side of the reflexed and altered portion of the pinnules, which serves as an indusium.

Pinnules triangular-oblong, bearing short sori on their inwardly reflexed margins which form the indusium.

In the east it is often dwarfedsix to ten inches high, growing in tufts with stout rootstocks, having the pinnules finely toothed instead of rounded and the indusia often lunate, rarely twice as long as broad.

Pinnules, fan-shaped on slender, black stalks, long, deeply and irregularly incised.

Veins extending from the base of the pinnules like the ribs of a fan.

Pinnæ sub-opposite, divergent, narrowly oblong, obtuse; base truncate, cordate or clasping, occasionally auricled; lower pinnæ often with orbicular or cordate pinnules.

Pinnules distant, the reflexed, narrow margin forming a continuous, membranous indusium.

Pinnules divided into minute, densely crowded segments, the herbaceous margin recurved and forming an almost continuous indusium.

Notholàena Small ferns with fruit-dots borne beneath the revolute margin of the pinnules, at first roundish, but soon confluent into a narrow band without indusium.

Pinnules pinnately cleft, the oblong lobes spinulose-toothed at the apex.

Inferior pinnules on the lower pair of pinnæ conspicuously elongated.

In outline the fragile bladder fern suggests the blunt-lobed Woodsia, but in the latter the pinnæ and pinnules are usually broader and blunter, and its indusium splits into jagged lobes.

incìsa has the inner pinnules of some of the pinnæ more or less cut-toothed.

Pinnules lanceolate, strongly decurrent so that the pinnæ are merely pinnatifid.

[Illustration: Fruiting Pinnules of Filmy Fern (From Waters's "Ferns." Henry Holt & Co.)]