Colleagues,
Recently I requested ideas on seeds which would show the remnant of the
nucellus (megasporangium). Pinyon pine seeds were suggested, as were other
pines. Castor beans were suggested also, I think mainly for showing the
features of seeds in general and perhaps not as a seed in which one could
observe nucellar remains. Most of the responses after that dealt with the
danger of ricin, the toxin present in castor bean seeds.
Not having immediate access to either pinyon pine or castor bean, I tried a
modification of Virginia Berg's idea on modeling flowers. I brought in
play-do and had the students construct their own seed, complete with thin
nucellar layer, integument, embryo, etc. Then they made a longitudinal
section with a spatula which showed all the various layers, and I had each
student identify them for me along with the ploidy level and generation
(sporophyte/gametophyte). This worked really well to give the students a
3-dimensional feel for the structures, plus made a connection between the
3-D object and the 2-dimensional board drawings. If students wished, I let
them take their "seed" home to dry out and use as a study guide. I was
happy with how it worked out - the students were a little surprised at
first, but really got into it.
Thanks to all who responded to my request, and thanks to Virginia for the
original idea.
Kathleen Archer
