FURTHER OBSERVATIONS ON THE STRUCTURE OF SELAGINELLITES CRASSICINCTUS

LEISMAN, GILBERT A. (Kansas State Teachers Coil., Emiporia.) Further observatioins on the structure of Selaginellites crassicinctus. Amer. Jour. Bot. 48(3): 224-229. Illus. 1961.-Specirnens of Selaginellites crassicinctus Hoskins and Abbott in coal balls from southeastern Kansas have yielded new information concerning the anatomy of this strobilus. The axis contains an exarch protostele apparently suspended in an air-cavity by endodermal trabeculae. Sporophylls are attached in alternating whorls of 4 each. The strobilus is compared with modern Selaginellh and a related compression fossil species. THE HERBACEOUS lycopod genus, Selaginellites, has always evoked considerable interest among paleobotanists because of the intriguing morphological similarities between it and the modern genus, Selaginella. Selaginellites was proposed by Zeiller (1906), on the basis of compression material, to include herbaceous lycopods exhibiting heterospory. Most specimens subsequently assigned to this genus (Halle, 1908; Lundblad, 1948; Chaloner, 1954, 1958) have also been of a compression nature. Comparisons of these species with Selaginella were hence, of necessity, restricted to external characteristics and the morphology of the spores. The first anatomical data to be added to our knowledge of this genus was provided by Hoskins and Abbott (1956) who described the species. Selaginellites crassicinctus, as preserved in a coal ball from the Flerniing coal, collected about 4 mi. southwest of West Mineral, Kansas. This specimen, which consisted wholly of a strobilus, or a portion thereof, was unfortunately not too well preserved. Details of the microspores and megaspores, of their sporangia and sporophylls, were evident and admirably described and illustrated, but little or no information could be obtained concerning the cone axis, the arrangement of the sporophylls on the axis (a spiral phyllotaxy was suggested), or the vegetative part of the plant to which this cone was attached. The strobilus was approximately 12 mm. long and 5 mm. wide, with ligulate sporophvlls attached to the axis nearly at right angles. Each sporophyll was supplied with a single vascular trace which extended almost to the tip. The sporangia were essentially spherical in shape, each being attached by a short, thick stalk to the abaxial side of the sporophyll. The megaspores, numbering 4 or 5 per megasporangium, were regarded as being conspecific with Triletes triangulatus Zerndt, while the microspores were conspecific with Cirr-atriradites annulatus Kosanke and Brokaw. I Received for publication July 25, 1960. Supported by a grant from the National Science Foundation (NSF G-6360). Specimens of this species recently found by the present author in coal balls fromr southeastern Kansas add considerably to our knowledge of the anatomy of Selaginellites and make possible some pertinent comparisons with Selaginella. Coal ball #51 contained isolated sporophylls with attached intact sporangia and a portion of a cone axis with attached sporophylls and empty sporangia. Most of the detailed information concerning the anatomy of the axis and the phyllotaxy of the sporophylls wvas obtained from this latter specimen. Coal ball #87 contained only detached sporophylls and sporangia. Coal balls #614, 658, and 761 con. tained intact cones or portions of' cones the general degree of preservation of which was only good enough, for the most part, to confirm partiallv observations obtained frorrm coal balls #51 and 87. Coal ball #51 was collected at the Kruger mine, I mi. north of Cherokee, Kansas. Coal ball #87 was collected at an old Pittsburg-Midway waste dump, 2 mi. northeast of Chero'-ee, Kansas. These two balls cannot be assigned with certainty to a particular coal seam but are undoubtedly from the Cherokee group, Desmoinesian series of the middle Pennsylvanian. Coal balls #614, 658, and 761 are from the Pittsburg-Midway mine, approxiimately 8 mi. southwest of West Mineral, Kansas. These can be assigned to the Fleming coal of the Cherokee group, the same stratum as that of the