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Calamocarpon Insignis, a New Genus of Heterosporous, Petrified Calamitean Cones from the American Carboniferous
Robert W. Baxter
American Journal of Botany
Vol. 50, No. 5 (May - Jun., 1963), pp. 469-476
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2440317
Page Count: 8
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Calamocarpon insignis is described as a new genus of calamitean cone based on numerous fragments of microsporangiate and megasporangiate cones found in coal balls of middle Pennsylvanian age from the Cherokee Group of Kansas and the Des Moines Series of Iowa. The cones are similar to Calamostachys in general construction, having a hollow pith, prominent protoxylem canals, and alternating whorls of sterile bracts and sporangiophores. They differ in that the microsporangiate cones bear microsporangia each containing several hundred microspores which may occur as tetrads or single spores, while the megasporangiate cones bear large rectangular megasporangia each containing a single functional megaspore surrounded by sterile nutritive tissue. The microspores average 30-40 μ in diameter compared to a maximum measurement of 2.7 x 0.7 mm for the single rectangular megaspore. The female gametophyte was produced within the megaspore which was held within the megasporangium during the entire period of development. The megasporangia were deciduous so that the entire structure was shed as a unit.
American Journal of Botany © 1963 Botanical Society of America, Inc.