This generic name was instituted by Brongniart[1254] for simple linear or broadly linear leaves with a prominent midrib from which secondary veins, simple or dichotomously branched, are given off at right angles or obliquely. The frond of the type-species Taeniopteris vittata ([fig. 332]), characteristic of Jurassic floras, was compared by Brongniart with the pinnules of Danaea and Angiopteris. Among recent ferns the Taeniopteris form of frond and venation is represented by Oleandra neriiformis, Asplenium nidus, and many other species. Though usually applied to fronds which there is good reason for regarding as simple leaves, the generic designation Taeniopteris has been extended to include pinnate fronds, e.g. the Upper Palaeozoic species T. jejunata Grand’Eury, and T. Carnoti Ren. and Zeill. ([fig. 330], A). The compound fronds from the Lower Coal-Measures of Missouri described by Dr White[1255] as T. missouriensis are characterised by decurrent and confluent Taeniopteroid pinnules. In a later reference[1256] to this plant White pertinently adds, “perhaps it belongs more properly in Alethopteris.”
Leaves of the Taeniopteris type are described by several authors as species of Oleandridium, Angiopteridium, Danaeites, Marattia, and other genera. In such species of Taeniopteroid leaves as have been dealt with in a former Chapter, the occurrence of sori justifies the substitution of a name denoting a close relationship to existing members of the Marattiaceae, but in the absence of fertile specimens the provisional designation Taeniopteris should be retained. It is often difficult to decide between Taeniopteris and Nilssonia as the more suitable name to apply to fragments of fossil leaves of Mesozoic age. Taeniopteris is, however, distinguished from the Cycadean genus by the greater prominence of the rachis, also by the dichotomous branching of the secondary veins, usually close to their origin and at varying distances between the axis of the frond and the edge of the lamina. The genus Taeniopteris, though most abundant in Rhaetic and Jurassic strata, occurs also in Upper Carboniferous and Lower Permian rocks. The generic name Macrotaeniopteris instituted by Schimper[1257] has been used for leaves differing only in size from the usual type of Taeniopteris, but there is no adequate reason for its retention.
The species included in Taeniopteris afford no satisfactory evidence as to their systematic position. It is obviously unwise to adopt such generic titles as Oleandridium, Marattiopsis, etc., merely because of resemblance in the venation of sterile fragments to Oleandra or Marattiaceous ferns.
Some specimens of Taeniopteris fronds described by Mr Sellards[1258] from Permian rocks of Kansas, which are referred to later, have furnished unconvincing evidence of reproductive organs.
Taeniopteris multinervis, Weiss. Fig. 329, A, B.
The late Dr Weiss[1259] instituted this species (which he designated Taeniopteris multinervia, though the specific name multinervis is constantly used) for a fragment of a leaf from the Lower Permian of Lebach characterised by numerous forked veins given off at right angles from a prominent rachis ([fig. 329], B). This type of frond is recorded from the Permian of Trienbach (Alsace) by Zeiller[1260], by Renault[1261] and Zeiller[1262] from the Upper Carboniferous of Autun, and from other localities. The lamina of the simple leaf reaches a breadth of 6 cm. and a length of 40 cm. ([fig. 329], A); the numerous secondary veins (25–36 per cm. of lamina) are either at right angles to the rachis or given off at an acute angle. The mesophyll consists of polygonal cells some of which are elongated at right angles to the surface of the lamina. A very similar form is described by Fontaine and White from the Permian of Virginia as T. Lescuriana[1263].
Fig. 329.
- Taeniopteris multinervis, Weiss. (⅚ nat. size. After Zeiller.)
- T. multinervis. (Enlarged. After Zeiller.)
- Lesleya Delafondi. (× 2. After Zeiller.)
It is futile to expect to be able to separate the numerous Taeniopteris leaves into well-defined species: all we can do is to group the specimens under different names, using as artificial distinctions such characters as the shape of the leaf, the number of veins per centimetre, and the prominence of the rachis. Another Virginian species of Permian age described by Fontaine and White[1264], T. Newberriana, is said to bear sori, but no satisfactory information is given as to the nature of these organs. Specimens referred with some hesitation to this species and to a similar species, T. coriacea, have been described by Sellards[1265] from material obtained from Permian beds in Kansas. The lamina of the simple linear fronds is characterised by the occurrence of small oval bodies half immersed in the substance of the leaf between the secondary veins ([figs. 330], D, E). One of these bodies is represented in an apparently dehisced condition in [fig. 330], D. Sellards suggests the possibility that these bodies are sporangia, but, as he points out, they afford no indication of cellular structure nor are they in direct connexion with the veins.