Linopteris.
The Upper Palaeozoic fronds included in this genus are more familiar as species of Dictyopteris. Potonié[1557] has, however, pointed out that the creation of this name by Lamouroux in 1809 for a genus of Brown Algae which is still retained, makes it advisable to fall back upon the designation Linopteris. Gutbier[1558] proposed the genus Dictyopteris in 1835: Linopteris was first used by Presl[1559] in 1838. The fronds so named are identical with species of Neuropteris except in the anastomosis of the secondary veins; Linopteris bears to Neuropteris the same relation as Lonchopteris bears to Alethopteris. As in Neuropteris, Cyclopteroid pinnules occur on the petioles of Linopteris, but the veins form a fine reticulum. Grand’Eury[1560] records the association of Linopteris Brongniarti with seeds belonging to the genus Hexagonocarpon, a fact which points to the Pteridosperm nature of the foliage.
Some fertile pinnules of Linopteris Schutzei (Roemer) are described by Zeiller[1561] from Autun as bearing on the under surface of the lamina two rows of long and pointed sporangia, probably united in groups. The presumption is that these are microsporangia.
Fig. 374 is a reproduction of a careful drawing, originally published by Zeiller[1562], of a pinnule of the type-specimen of Gutbier’s species Linopteris neuropteroides. This species differs from Linopteris obliqua, instituted by Bunbury[1563] for specimens obtained by Lyell[1564] from the Coal-Measures of Nova Scotia, in the smaller size of the meshes. Linopteris obliqua occurs in the Upper and Middle Coal-Measures of Britain; it is recorded by Zeiller from Asia Minor, by Lesquereux[1565] from Pennsylvania, and by other authors from several European localities. The pinnules frequently occur detached from the frond and like those of some species of Neuropteris were caducous. Linopteris is rare in British strata.
Fig. 374. Linopteris neuropteroides, Gutb. (Pinnule of type-specimen. Enlarged. After Zeiller.)