Pinnules Sentence Examples
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.
Polyp 7 has proof sense, 1 o c oduced as its first bud, 8; as its second bud, a7, motion and nutriwhich starts a uniserial pinnule; and as a third t i on, until its bud I', which starts a biserial branch (I I'-VI') medusoid nature that repeats the structure of the main stem and and organization gives off pinnules.
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.
Arms fork once to thrice, and bear pinnules on each or on every other brachial.Advertisement
It is, however, probable that a considerable group of true Ferns, allied to Marattiaceae, existed in Palaeozoic times, side by side with simpler forms. In one respect the fronds of many Palaeozoic Ferns and Pteridosperms were peculiar, namely, in the presence on their rachis, and at the base of their pinnae, of anomalous leaflets, often totally different in form and venation from the ordinary pinnules.
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.Advertisement
From Palaeozoic rocks a few fronds have been described, such as Pterophyllum Fayoli, P. Combrayi, Plagiozamites and the leaves of Todites, a genus which may often be recognized by the broad and relatively short bluntly-terminated pinnules.
Polyps 3 and 6, stomach, and become eloninstead of producing uniserial pinnules, gated and tentacle-like, have produced biserial branches (3, 3 showing great activity of 3 3, 3 4;6 1 -6 3), which give off uniserial movement.