The Botry- opterideae are chiefly known from petrified specimens; in the genus Botryopteris and certain species of Zygopteris we have a fairly complete g knowledge of all parts of the plant.
The genus Zygopteris, of which numerous Carboniferous and Permian species are known, likewise had a monostelic stem, but the structure of its vascular cylinder was somewhat complex, resembling that of the most highly differentiated Hymenophyllaceae, with which some species of Zygopteris also agreed in the presence of axillary shoots.
It is characteristic of Zygopteris and its near allies that two rows of pinnae were borne on each side of the rachis, at least in the fertile fronds.
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.
The genus Diplolabis of Renault, shows much in common with Zygopteris as regards anatomical structure, but resembles Corynepteris in possessing a synangic fructification.
- Zygopteris pinnata.
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.
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