vulpia at sonic.net
Mon Mar 23 14:44:08 EST 1998
In article <220.127.116.11.19980320155005.0068f0f0 at mail.trincoll.edu>,
Kathleen.Archer at MAIL.CC.TRINCOLL.EDU says...
>I'm teaching a course which surveys the plant kingdom, and I have taken an
>evolutionary approach. Coming up in 2 weeks I will be introducing the
>concept of the seed, and I have been thinking about an exercise which will
>illustrate to the students all the different components of the seed:
>integument, megasporangium (nucellus), embryo, etc. The 2 parts that I
>think might be hard to show in a real specimen are the integument and the
>nucellus (or remnant thereof) since in many seeds the nucellus is long gone
>by the time the seed is mature. I know in some seeds the seed coat has an
>inner and outer layer which may separate but are still derived from
>integument and I don't want to be inaccurate and call the inner layer
>nucellus if in fact it is not. I'm trying to find a seed where it is known
>that the layer within the seed coat is in fact nucellar in origin.
>I wonder if anyone can recommend a seed which could be dissected to show
>clearly and distinctly both the integument and the remnant of the nucellus?
> Something large and relatively easy to come by would be great.
>Thanks for any help,
How about pine seeds? If you can get original ones (not supermarket
pinolas) that still have the seed coat, open it up, and the papery
covering is nucellus. Of course, there is no endosperm! -N
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