Phyllopodia in Isoetes

[Tom]

Dear quillwort enthusiasts,
    In Isoetes, the term phyllopodia seems to always refer to the reduced, scale-like leaves found on the outermost portion of the corm where they seem to persist longer than typical sporophylls. If new leaves are being produced centrally on the corm and gradually "pushed" outward, this would suggest that the same is true for the phyllopodia. If so, they seem not to be noticed until their normally darkened color is evident on the outside of the corm. Can anyone confirm this or suggest an alternative? I'm also interested in the utility of presence or absence of phyllopodia as a taxonomic character. Any thoughts would be appreciated.

Thomas F. Wieboldt, Assoc. Curator
Massey Herbarium
Dept. of Biology
VPI & SU, Blacksburg, Va. 24061