In this way are formed the familiar feathery colonies of Plumularia, in which the pinnules are all in one plane, while in the allied Antennularia the pinnules are arranged in whorls round the main biserial stem.
The pinnules never branch again, since in the uniserial mode of budding a polyp never forms a second polyp-bud.
Solitary polyps are unknown in this sub-order; the colony may be creeping or arborescent in form; if the latter, the budding of the polyps, as already stated, is of the sympodial type, and either biserial, forming stems capable of further branching, or uniserial, forming pinnules not capable of further branching.
- Hydrothecae sessile, biserial on the main stem, uniserial on the lateral branches or pinnules, which give the colony its characteristic feathery form; with nematophores.
Long with a rounded crenate outer edge and repeatedly forked veins; the sori (or masses of spore-capsules) are in the crenatures of the pinnules, and are protected by a kidney-shaped involucre.
5); the segments, which are broadly ovate or rhomboidal, have several forked spreading veins, and resemble the large pinnules of some species of Adiantum.
Food brought to the mouth by a subvective system of ciliated grooves, radiating from the mouth either between the plates of the theca (endothecal), or over the theca (epithecal), or along processes from the theca (exothecal: arms, pinnules, &c.), or, in part, and as a secondary development, below the theca (hypothecal).
Arms fork once to thrice, and bear pinnules on each or on every other brachial.
These curious appendages (Aphlebiae), at first regarded as parasitic growths, have been compared with the feathery outgrowths which occur on the rachis in the Cyatheaceous genus Hemitelia, and with the 'anomalous pinnules found in certain species of Gleichenia, at the points of bifurcation of the frond.
The type-genus Botryopteris, represented in the Permo-Carboniferous of France and in both the Lower and Upper Carboniferous of Great Britain, had a rhizome, with a very simple monostelic structure, bearing spirally arranged compound leaves, with lobed pinnules, probably of a somewhat fleshy texture.
This Jurassic species bore bipinnate fronds not unlike those of the South African, Australian, and New Zealand Fern Todea barbara, which were characterized by a stout rachis and short broad pinnules bearing numerous large sporangia covering the under surface of the lamina.
This type is distinguished by its large bipinnate fronds bearing long and narrow pinnae with close-set pinnules, characterized by the anastomosing secondary veins.