Root hairs and dangly thingies in floating plants

["Karpa-Wilson, Douglas" <dkarpawi at indiana_edu>]

> Subject: Re: Please help finish this sentence
> 
> ... Help please and feel free
> to correct me or suggest a term while you're at it.
 
> "Floating Plants - Plants which float on the surface of the water,
> deriving needed nutrients from the water via hairlike structures
> called ______. "

> The answer is--------root hairs

}"Thallus" and "leaves" would also be correct. e.g. : Riccia and
}megaphylls
}Myriophyllum, the microphylls of moss.

}Hairlike structures, absorb nutrient through these structures, can
}float on
}the water. 

}Regards, 
}Tom Barr


Hey, all,

Until Tom posted I hadn't really read the original posting.  Actually,
"root hairs" isn't correct.  Root hairs are very small (usually
microscopic) protruberances from epidermal cells of angiosperm roots (at
least I think only angiosperms produce them), so the visible dangly
things in the case of duckweed and other flowering plants that float are
probably just roots.  These roots may also have root hairs on them, but
they wouldn't be visible to the naked eye.  In the case of ferns and
floating mosses, they'd be called something else, although I'd guess
their anatomy is a little tweaked from the usual fern anatomy.  A
thallus refers to the undifferentiated vegetative mass of mosses,
liverworts, fungi, etc., that does not have leaves, stems and roots,
i.e. the gametophyte, haploid generation, which in the case of
liverworts (like Riccia) and mosses, that's what we're looking at.  In
the case of ferns like Salvinia or Azolla, they'll be megaphylls or
simple roots.

So the short answer is:  it depends on what the plant is.