Carol-
I've got several suggestions for your spring plant i.d. course:
-- regarding the point about students dissecting plants before they've seen them
in lecture: I don't have a problem with this and do it all the time in my
class. In fact, I think it makes more sense to talk about the evolution of
plant family traits after students have seen them in lab. You might consider
using an excellent text by Wendy Zomlefer, Guide to Flowering Plant Families, to
help students work their way through unfamiliar families. It has the best
illustrations I've seen and an extremely helpful illustrated glossary.
-- regarding preservation of flowers for use in class: I teach Plant
Systematics in the fall in central Minnesota. Since our quarter doesn't start
until late Sept., we've almost always had a killing frost before we even get
started. So to provide students with representatives of a large number of
families I freeze flowers from spring onward to use in my course. To do this, I
pick single flowers (except in those species with tiny flowers, e.g. Galium,
some mints and mustards, etc.), package them in sandwich-sized ziplock bags
along with a folded paper towel to absorb excess moisture and a label indicating
family, genus and species, and freeze them in an upright freezer. I pick enough
flowers to provide about 1.5 times the number of students per section for each
bag (multiple sections = multiple bags of each species). Then when it's time
for lab I take out the unknows for the day, substitute a numbered label for the
i.d. label, and put them in a small freezer in the classroom. I have also
developed a collection of pressed specimens of the species I use every year that
are mounted and labeled with all of the typical information EXCEPT for family,
genus and species. My sections typically run about 18 students, and I have one
pressed specimen for every 2-3 students. Using this system students pick up a
pressed specimen from which they can glean relevent vegetative characters,
information about inflorescence type, etc. and a frozen flower to dissect, then
run the species through their key. Most flowers, except the most delicate ones,
hold up very well this way and are easy to dissect as they thaw. The reason for
having several different bags (one for each lab section) is to ensure good
quality specimens for each student, since the flowers don't hold up well once
they have thawed completely. Finally, the frozen flowers maintain their good
condition for a long time in the freezer -- I have used flowers that have been
frozen for over 2 years, though they eventually dessicate, succumbing to
"freezer burn," and are less useful.
-- regarding the size of student plant collections: I think 20-25 plants is
sufficient to achieve the objectives of the assignment. I have students mount
only 5 of their plants (preparing labels for all but handing in most in
newspaper), and instruct them to choose the 5 that they believe are their best
specimens and ones that will contribute most to building our student herbarium
(i.e., those that they find are underrepresented) since we need only so many
specimens of the commonly collected species such as Nepeta cartarica, Solidago
canadensis etc.!
Margaret
Margaret A. Kuchenreuther
Associate Professor of Biology
Division of Science and Mathematics
University of Minnesota - Morris
600 East 4th St.
Morris, MN 56267
Phone: (320) 589-6335 or -6300 (message)
FAX: (320) 589-6371
email: kuchenma at mrs.umn.edu
