ANACHOROPTÉRIS INVOLUTA AND ITS ATTACHMENT TO A TUBICAULIS TYPE OF STEM FROM THE PENNSYLVANIAN OF IOWA

HALL, JOHN W. (U. Minnesota, Minneapolis.) Anachoropteris involuta and its attachment to a Tubicaulis type of stem from the Pennsylvanian of Iowa. Amer. Jour. Bot. 48(8): 731-737. Illus. 1961.-Petioles referable to Anachoropteris involuta are described, attached to a stem which most nearly corresponds to a member of the genus Tubicaulis. These petioles are attached in a 2/5 phyllotaxy. At their points of departure petiole traces are massive and C-shaped but become involute in regions away from their attachment. Adventitious roots were borne on the stem in partial whorls. It is suggested that 4nachoropteris petioles were extremely long and that they bore adventitious stems at intervals. These, in turn, bore adventitious roots, perhaps to serve for uptake of minerals or support in regions removed from the true stem. Such a "petiole unit" may also have functioned as a vegetative propagule. This would account for the apparent rarity of true stems and the abundance of petioles in coal balls. ALTHOUGH one of the less conspicuous elements of the Paleozoic vegetation, the coenopterid ferns nevertheless occurred in great variety. Two incompletely or inadequately known form genera of this group are Tubicaulis and Anachoropteris. Tubicaulis is a generic name assigned to protostelic stems to which are attached baror C-shaped petiole traces in a 2/5 phyllotaxy; except for their bases, where attached to the axis, the leaves of Tubicaulis are unknown. On the other hand, Anachoropteris is a genus which includes petioles whose xylem traces are more or less involutelv coiled, with the bar portion of the trace presumably on the adaxial face of the petiole. These petioles are not infrequently encountered in coal balls, but there has been only 1 account of either fructifications or foliage laminae attached to supposed Anachoropteris petioles (Kubart, 1916). The axis to which petiales of the Anachoropteris type were attached is unknown, but there have been suogestions that Tubicaltlis or Tubicaulis-like stems did bear Anachoropteris petioles (cf. Delevoryas and Morgan, 1954). In no specimen of Tubicaulis thus far recorded have the petiole traces been involute, in typical Anachoropteris fashion. Delevoryas and Morgan (1954) have discovered petioles of A, clavata to which are attached small, terete, stem-like axes. But for other species of Anachoropteris, no principal axis has been discovered. Tubicaulis is represented by 6 species, 3 known from Europe, 3 from the United States; 2 growth habits are represented in this genus: an erect, perhaps somewhat shrubby habit, and the scan;dent habit. From this country, T. multiscalariformis Delevoryas and Morgan (1952) and T. stewartii I Received for publication March 6, 1961. Support for this publication was provided by grant G944 from the National Science Foundation. Appreciation is expressed to Chr. Westergaard, Danish Geological Survey, who made the photographs. Eggert (1959) are erect, and T. scandens Mamay (1952) is an epiphyte on a trunk of Psaronius. There are relatively few specimens of Tubicaulis known; 2 of the American species are based on single specimens. Anachoropteris is much commoner than Tubicaulis and many species are known. A. involuta Hoskins (1930) is particularly common in this country. The stem to be described here is essentially a Tubicaulis stem, but petioles of the Anachoropteris involuta type are attached to it. It is convenient in the following description to refer to the stem as Tubicaulis and to the petioles as A. involuta. The stem does not correspond to any of the species of Tubicaulis thus far described. This stem is from a coal ball collected at the Carbon Hill coal mine near Oskaloosa, Iowa, which is in the Des Moines Series of the Middle Pennsylvanian. The coal ball was relatively small and oblate, and the axis lay obliquely to its long axis. Since the coal ball was cut at right angles to its long axis the stem was originally cut somewhat obliquely; subsequent cuts partially corrected the obliquity. The ends of the stem, at the margins of the coal ball, were pyritized and not well preserved. In spite of its small size the coal ball contained numerous plant fragments, mostly leaves, cones and seeds of Cordaites. Delevoryas and Morgan (1952) suggested a semisubterranean habit for T. multiscalariformis, partly on the basis of lack of associated extraneous material. It would appear likely that the present stem was an aerial segment which was transported and deposited with the other associated aerial plant fragments; neither apex nor base was preserved. DESCRIPTION OF THE SPECIMEN-The stem was probably sub-elliptical in outline, but Fig. 1, 2, 10, 11 appear elliptical because of a slight obliquity to the sections and because the specimen has been