The sporangia are borne in groups (sori) on the under surface of the leaves; sometimes the fertile leaves differ more or less from the purely vegetative ones.
Sori, s, on its back.
Sori) for which Gilead was so noted (Gen.
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.
In Todea the sori, each of which consists of a single circle of bulky sporangia, are borne on the under surface of the pinnae.
The sporangia are borne singly or in sori of two or three on the margin or under surface of leaves, the fertile pinnae of which differ more or less from the sterile segments.
The sori ale borne on the under surface of the pinnae, in the D (From Strasburger's Lehrbuch der Botanik.) FIG.
The elongated receptacle of the marginal sori is surrounded by a basal cup-shaped indusium.
The sori, which are marginal, have a long receptacle, bearing the sporangia in basipetal succession, and are surrounded by a cup-shaped indusium.
The sporangia in both genera are associated in sori enclosed by indusia springing from the base of the receptacle.
The sori are developed in depressions and are thus protected within the resistent outer wall of the sporocarp. There are usually four sori in Pilularia, while in Marsilia they form two longitudinal rows.
If infection takes place, other sori are formed in ten days or a fortnight under favourable conditions of moisture and warmth.
Typically Marattiaceous sori, consisting of exannulate sporangia united to form synangia, are frequent, and are almost always found on fronds with the character of Pecopteris, large, repeatedly pinnate leaves, resembling those of Cyatheaceae or some species of Nephrodium.
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.
The genus Corynepteris of Baily is interesting from the fact that its sporangia, while individually similar to those of Zygopteris, were grouped in sori or synangia, resembling those of an Asterotheca.
Another form of fructification, compared to the sori of Dicksonia, appears to represent the male organs.
Leaving out of account the numerous sterile fronds which cannot be certainly referred to particular families of Ferns, there are several genera which bear evidence in their sori, and to some extent in the form of the leaf, of their relationship to existing types.
The abundance of Palaeozoic plants with sporangia and sori of the Marattiaceous type is in striking contrast to the scarcity of Mesozoic ferns which can be reasonably included in the Marattiaceae.
Names are sterile, and can not be assigned to a particular family, but some are undoubtedly sporangia with an apical annulus (" monangic sori " of Prantl) on either side of the midrib.
On the other hand, there are several fossil Ferns of Jurassic age possessing cup-like sori like those of Thyrsopteris and other Cyatheaceous Ferns, which indicate a wide Mesozoic distribution for this family.
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.
No traces of sori have so far been found on the fronds.
In Dictyota the oospheres arise singly in oogonia, crowded together in sori on the surface of the female plant.
The sporangia (pollen-sacs), which occur on the under-side of the stamens, are often arranged in more or less definite groups or sori, interspersed with hairs (paraphyses); dehiscence takes place along a line marked out by the occurrence of smaller and thinner-walled cells bounded by larger and thickerwalled elements, which form a fairly prominent cap-like " annulus " near the apex of the sporangium, not unlike the annulus characteristic of the Schizaeaceae among ferns.
2, h) the sori are borne towards the base of the submerged leaves, in A zolla on the reduced ventral lobe of the leaf.