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In lab today - clubmosses

Clubmosses are a favorite group of plants, the oldest lineage of living vascular plants, relicts of the Devonian and Carboniferous, a glimpse into the primeval world.  What a great group of organisms.  They retain all sorts of features that used to be commonplace, but presently are unusual.  They exhibit dichotomous branching, an equal branching into two axes, both the stems and roots.  They have microphyllous leaves, leaves with a different origin than all the rest of vascular plants, although that origin is a bit uncertain.  The morning was spent rounding up all the specimens, fossils, slides, perserved specimens, herbarium specimens, and live specimens.  Integrating all of this is an educational challenge for the students, but e-portfolios in lieu of lab reports seems to help.  The specimen show is a bit of an aerial shoot of Selaginella pallescens.  It's an upright species that has its sporangia aggregated at the ends of shoots and somewhat differentiated sporophylls producing strobili, cones, with both megaspores and microspores in separate sporangia, and with some care they can be cultured into mature gametophytes, which after fertilization will produce new sporophytes. 

2 comments:

JaneB said...

Selaginella is cool (and both its microspores and megaspores are easy to identify when they turn up in sediments, which makes me like it all the more...)

The Phytophactor said...

Sediments? You sure you didn't find microspores and megaspores of Isoetes, quillwort, which is aquatic?