Horsetails morphologically appear to be microphylls today. However,
they evolved through reduction of megaphylls, and they are not
homologous with the microphylls of lycopsids. Therefore, the correct
answer depends on what you want to communicate.
I don't place a great deal of credance into leaf gaps because I think
they can be an artifact of some stelar arrangements. But for those who
are interested, Gifford and Foster (1989. Morphology and Evolution of
Vascular Plants), page 187, has a diagram of Equisetum vascular anatomy,
and I could see an interpretation that it does have leaf gaps.
Doug
-----
Douglas P. Jensen
Assistant Professor and Chair
Biology Department
Converse College
580 E. Main St.
Spartanburg, South Carolina 29302
(864)596-9123
-----Original Message-----
From: "Janice M. Glime" [mailto:jmglime at mtu.edu]
Sent: Wednesday, September 24, 2003 9:55 PM
To: plant-ed at net.bio.net
Subject: Re: horsetail leaves
Scott,
There are no leaf gaps and only one vein per leaf, making them
microphylls. To my knowledge, there are no exceptions. Ferns are the
first group to have macrophylls, even though horsetails have a
siphonostele.
Janice
***********************************
Janice M. Glime, Professor
Department of Biological Sciences
Michigan Technological University
Houghton, MI 49931-1295
jmglime at mtu.edu
906-487-2546
FAX 906-487-3167
***********************************
On Wed, 24 Sep 2003, Scott Shumway wrote:
> Are horsetail leaves microphylls or megaphylls? I've seen references to both.
> --
> Scott Shumway
> Professor of Biology
> Dept. of Biology
> Wheaton College
> Norton, MA 02766
> 508-286-3945
>sshumway at wheatonma.edu> fax 508-285-8278
>>> ---
>---
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