Another form of fructification, compared to the sori of Dicksonia, appears to represent the male organs.
The species differ greatly in size and general appearance and in the character of the frond; the sori or groups of spore-cases (sporangia) are borne on the back of the leaf, are globose and naked, that is, are not covered with a membrane (indusium) (see fig.
In Dictyota the oospheres arise singly in oogonia, crowded together in sori on the surface of the female plant.
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.
The sori are borne on the under surface of the pinnae, usually in a single row on either side of the midrib, but in Kaulfussia dotted over the expanded lamina.
The sporangia in both genera are associated in sori enclosed by indusia springing from the base of the receptacle.
The sori ale borne on the under surface of the pinnae, in the D (From Strasburger's Lehrbuch der Botanik.) FIG.
Genus, ranging throughout the Carboniferous, the elongated sporangia individually resemble those of Marattiaceae, but they are completely isolated, the characteristic grouping in sori being absent; the same remark applies to the Sphenopteroid Renaultia of Zeiller (fig.
Numerous more or less isolated fern-sporangia occur in the petrified material of the Carboniferous formation; the presence of an annulus is a frequent character among these specimens, while synangic sori are rare; it is thus certain that families remote from the Marattiaceae were abundantly represented during this period.
There are, indeed, a certain number of species which show traces of sori like those of modern species of Asplenium and other genera, but in most cases the names of recent ferns have been used on insufficient grounds.