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Studies on Fossil Azolla: Primitive Types of Megaspores and Massulae from the Cretaceous

John W. Hall
American Journal of Botany
Vol. 56, No. 10 (Nov. - Dec., 1969), pp. 1173-1180
Stable URL: http://www.jstor.org/stable/2440779
Page Count: 8
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Studies on Fossil Azolla: Primitive Types of Megaspores and Massulae from the Cretaceous
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Abstract

Fossil Salviniaceae are described from the Claggett Shale and Judith River Formation, late Cretaceous (Campanian stage) of Montana. A new genus, Parazolla, from the Claggett Shale, has megaspores in which the swimming apparatus is composed of a number of elongate floats attached to the megaspore body and invested by coiled hairs. The floats separate at maturity. Massulae (bearing microspores) have simple hair-like glochidia, many of which are knobbed at their tips. Glochidia tend to resemble the perisporial hairs of the megaspore body. This resemblance provides fossil evidence of the homology of these two hair-like structures among living species of Azolla. In Azolla simplex from the Judith River Formation the megaspore has a single cap-like so-called columellate float. Massulae, which have anchor-shaped glochidia, are associated with these megaspores. A. simplex is the oldest species of Azolla and Parazolla the oldest member of the Salviniaceae so far found.

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