In one member of the Medulloseae, there is direct evidence of reproduction by seeds, for in Neuropteris heterophylla Kidston has demonstrated that large seeds, of the size of a hazel-nut, were borne on the frond (fig.
Finally, in the pinnae of the frond the centrifugal xylem may disappear, the protoxylem being now exarch in position and abutting on the phloem.
The leaves, borne on the regions between the false dichotomies, are those of Anomozamites minor, a type of Cycadean frond originally determined FIG.
The large frond of Cycadites represented in fig.
Continuity between seeds and frond was also demonstrated in another species, A.
In Stauropteris, a genus showing some affinity with Zygopteris, the branched rachis of the fertile frond terminates in fine branchlets, each bearing a single, spherical sporangium, without any differentiated annulus (fig.
E, Vertical section of frond of the complicated Siphoneous Green Alga Halimeda.
This is the case in the Fucaceae, and in a very marked degree in the Laminariaceae in question, where the assimilative frond is borne at the end of an extremely long supporting and conducting stipe.
The substance of the frond is made up by a single much-branched tube, with interwoven branches.
One large specimen is figured by Heer from Lower Cretaceous rocks of Greenland, and by the side of the frond is shown a carpel with lateral ovules, as in the female flower of Cycas; but an examination of the type-specimen in the Copenhagen Museum led the present writer to regard this supposed carpel as valueless.