Two Species of Alethopteris from Iowa Coal Balls
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Proceedings of the Iowa Academy of Science Volume 83 Number Article 4 1976 Two Species of Alethopteris From Iowa Coal Balls Mary Ann Reihman University of Iowa J. T. Schabilion University of Iowa Let us know how access to this document benefits ouy Copyright ©1976 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Reihman, Mary Ann and Schabilion, J. T. (1976) "Two Species of Alethopteris From Iowa Coal Balls," Proceedings of the Iowa Academy of Science, 83(1), 10-19. Available at: https://scholarworks.uni.edu/pias/vol83/iss1/4 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact [email protected]. Reihman and Schabilion: Two Species of Alethopteris From Iowa Coal Balls Two Species of Alethopteris From Iowa Coal Balls MARY ANN REIHMAN and J. T. SCHABILION1 REIHMAN, MARY ANN, and 1. T. SCHABILION (Department of Botany, fem-like compression foliage. Most subsequent studies of the genus have been University of Iowa, Iowa City, Iowa 52242). Two Species of Alethopteris from confined to compression material. A summary of this work is found in Wagner's Iowa Coal Balls. Proc. Iowa Acad. Sci. 83(1): 10-19, 1976. comprehensive monograph ( 1968). Alethopteris sullivanti (Lesquereux) SYNPOSIS: Petrified specimens of Alethopteris sullivanti (Lesquereux) Schimper and Alethopteris lesquereuxi Wagner are the only Pennsylvanian Schimper and Alethopteris lesquereuxi Wagner, species of Pennsylvania seed species of which the details of internal anatomy are known from petrified coal fem leaves, were found in coal balls from the Lovilia locality in south central ball material (Leisman, 1960; Baxter and Willhite, 1969). Iowa. The morphology and anatomy of these leaves are described and are Wagner ( 1968, pp. 16-17) believes that the classification of Carboniferous compared with findings of previous workers (Leisman, 1960; Baxter and Will fem-like foliage into natural genera must be based on several different features. hite, 1969). These are I) the general morphology of the frond and its pinnae, 2) epidermal It is generally accepted thatAlethopteris is a foliage type of the Pennsylvania characteristics as preserved in cuticles, 3) fructifications, 4) pinnule morphol pteridosperm, Medullosa (Scott, 1899; Steidtman, 1944). Evidence cited to ogy and ontogenetic pattern. Wagner feels that ultimately studies of cuticles will support this includes the attachment of seeds to Alethopteris foliage (Halle, be particularly useful in establishing natural genera. 1927), the common association of the genus with Myeloxylon, Dolerotheca, This paper describes the morphology and anatomy of Alethopteris sullivanti Pachytesta, and other organ genera of medullosan affinity, and the anatomical andA. lesquereuxi leaves found in Iowa coal balls. It also includes a study of the similarities of the leaves with Myeloxylon petioles (Leisman, 1960; Ramanu jam cuticles of these species. et al., 1974). INDEX DESCRIPTORS: Paleobotany; fossil plants; Alethopteris; coal balls; The genus, Alethopteris, was established by Sternberg in 1825 to describe a Iowa Pennsylvanian. MATERIALS AND METHODS cm at the pinnule border. The secondary veins depart from the mid rib at acute angles and dichotomize once or twice as they arc to the The petrified specimens used in this study were found in coal balls margin. The midrib is present only in the basal two-thirds of the collected from the Lovilia locality in south central Iowa. This locality is pinnule and appears slightly decurrent at its attachment to the rachis believed to be stratigraphically equivalent to the Summon (No. 4) coal (Fig. 7, 9). Several subsidiary veins enter the basioscopic side of the of Illinois and the Bevier coal of Kansas (Schabilion et al., 1974). pinnule (Fig. I, 8). Upon sectioning the Lovilia coal balls hundreds of alethopteroid As has been noted by other workers (White, 1899; Leisman, pinnules were found. Splitting coal balls along their internal bedding 1960), the basal pinnules differ slightly in morphology from the planes, as outlined by Leisman ( 1960), revealed the external mor more apical ones. The basal pinnulcs are constricted at the base hav phology of the pinnules. This made possible comparison of the pin ing a neuropteroid-type attachment to the rachis (Fig. 10). These nules with compression specimens and allowed correlation of pet pinnules measure 28 X 12 mm. rified and compression specimens. The internal anatomy of the pin INTERNAL ANATOMY - In transverse section the pinnules of nules was studied by using standard cellulose acetate peels (Steward Alethopteris sullivanti are relatively flat (Fig. 3, I I). The general and Taylor, 1965). outline of the pinnule is smooth, and the only ridge on the lower The cuticle and epidermis of petrified pinnules was studied by surface is that of the midrib which, as has been noted, is present macerating coal ball fragments with a dilute HC I solution. If pyrite only in the basal two-thirds of the pinnulc. In the flat portion of the obscured the cuticles, they were cleared with Schultz's solution blade the pinnules average 537 µ in thickness, while in the midvein (Brown, 1960). The cuticles were then mounted on microscope area they average 888 µ in thickness. slides in Piccolyte. A thick cuticle (~5 µ) covers the upper surface of the pinnule. The specimens and slides illustrated in this paper arc housed in the The upper epidermis is composed of small rectangular cells which palcobotanical collections of the University of Iowa. average 19 µ X 25 µ (Fig. 2, 12). A hypodermis of large, squarish cells (41 µ X 39 µ)underlies the epidermis. The mesophyll of the ALETHOPTERIS SULLI V ANTI pinnule consists of both palisade and spongy parenchyrna (Fig. 2, EXTERNAL MORPHOLOGY - The specimens found by split ting Iowa coal balls (Fig. 7) are comparable to compression speci mens of Alethopteris sullivanti (Lesquereux) Schimper (Fig. 9). The Key to Labeling: b, bundle sheath; c, secretory canal; e, bundle sheath exten specimens shown in figures 7 and 9 exhibit the characteristics of the sion; f?, xuard cell; h, multicellular hair; hb, hair base; hy, hypodermis; I, lower epidermis; m, midrib; p, palisade parenchyma; pa, papillae; r, rachis; s, species as outlined by Wagner ( 1968): Typically the pinnules are sponxy parenchyma; sc, sclerenchyma; st, stoma; u, upper epidermis; v, vein; obliquely inserted and broadly confluent at the base. They are vb, vascular bundle; x, xylem. strongly dccurrent on the basioscopic side and generally are con stricted at the acroscopic side. The pinnulcs range from 12-24 mm Fig. 1-6 - Fig. I. Diagram of a single pinnule of Alethopteris sullivanti long by 7-12 mm wide. (redrawn from Wagner, 1968) XS. - Fig. 2. Diagram of A. sullivanti in Closer examination of a single pinnulc (Fig. 8) obtained from an transverse section showing a single vascular bundle and the anatomical features Iowa coal ball shows the venation characteristic of Alethopteris .ml of the pinnule. X200. - Fig. 3. Outline of A. sullivanti in transverse section livanti (Fig. I). The density of secondary veins is 22-25 veins per drawn from fig. 11. XS. - Fig. 4. Outline of A. lesquereuxi in transverse section drawn from fig. 27. XS. - Fig. S. Diagram of pinnules of A. les quereuxi. (redrawn from Wagner, 1968) XS. - Fig. 6. Diagram of A. les quereuxi in transverse section showing a single va~cular bundle and the anatom 'Department of Botany, University of Iowa, Iowa City, Iowa S2242 ical features of the pinnule. X200. Published by UNI ScholarWorks, 1976 1 Proceedings of the Iowa Academy of Science, Vol. 83 [1976], No. 1, Art. 4 ALETHOPTERIS FROM COAL BALLS 11 • ' T I 1 ~I l I ~ I ~. 1 . , . ,. • , • . .,,... -'-u:. ~ T • ..--" .,. https://scholarworks.uni.edu/pias/vol83/iss1/4 2 Reihman and Schabilion: Two Species of Alethopteris From Iowa Coal Balls 12 PROC. loWA ACAD. SCI. 83 (1976) 12). The palisade parenchyma consists of 2, possibly 3, layers of areas which are believed to be the bases of multicellular hairs which cells which often contain a dark material. The palisade cells are ver have broken off (Fig. 24). These occur most commonly on the mid tically elongated, each averaging 72 µ X 27 µ (Fig. 13). As Leisman rib and on the secondary veins proximal to the midrib. The hair noted, approximately one-third of the mesophyll layer consists of bases are quite large and cover l, 2, or 3 lower epidermal cells. palisade cells. The remaining two-thirds is spongy parenchyma. The spongy parenchyma cells are irregular in shape and have "arms" ALETHOPTERIS LESQUEREUXJ extending in various directions. This gives the cells a stellate appear ance. Numerous air spaces are present in the tissue (Fig. 14). The EXTERNAL MORPHOLOGY - The fractured surface of coal lower epidermis is composed of a single layer of small rectangular balls revealed the external morphology of Alethopteris lesquereuxi cells averaging 18 µ X 27 µ (Fig. 2, 12). These observations are pinnules (Fig. 25, 26). These pinnules fit the species description similar to those made by Leisman ( 1960). given by Wagner: The pinnules have a pecopteroid aspect. They are In the basal portion of the pinnule, the midrib is quite prominent inserted almost at right angles to the rachis, fairly widely spaced, (Fig. 16). Most of the cells in the midrib are large and thin-walled. and narrowly confluent at the base. They are elongate-triangular in Leisman suggested that these cells may represent a proliferated bun shape and range 6-20 mm long by 4-5 mm wide. The margins of the dle sheath. A crescent-shaped band of sclerenchyma 2-3 cells thick pinnules are fairly straight and taper to an "obtusely acuminate borders the entire abaxial margin of the midrib; there is a square apex".