Dispersal Lab Topic 22
As part of laboratory Topic 20 we will discuss the mechanisms of seed
dispersal. There are five ways by
which seeds are dispersed after they have matured on the plant.
The five ways are:
by wind, characterized by the presence of wings (maple, elm), tufts of
hairs (milkweed, dandelions)
by water, typical of plants that live near streams and ponds and
characterized by the presence of wings and tufts of hairs
by the plant (explosively) characterized by fruit that "pops"
open and shoots out the seed when it is mature (jewelweed, touch-me-not,
by animals (actively, ingestion) characterized by the presence of tasty
seed coverings (apples, berries)
by animals (passively, carried on body) characterized by the presence of
hooks and barbs on the outside of the fruit (cocklebur, beggar's ticks).
lieu of the lab quiz on Tuesday 31 October, Wednesday 1 November or
Thursday 2 November you need to prepare a collection of 25 different seeds
that demonstrate as many of these dispersal mechanism as possible.
The seed collection will count 20 points (twice normal).
The seeds should be obtained from your homes, gardens, woods, fields,
vacant lots, etc. Do not purchase seeds or fruits and use these as part of the
collection! These seeds will be
unacceptable. Seed collections must be turned in during your scheduled
Each seed should be fastened to a 3 x 5" index card with double
sided tape or, if it is too large, placed in a small plastic zip-lock (sandwich)
bag with the card. The card should
indicate 1) date of collection, 2) name of the plant, 3) brief description of
the plant, 4) a description of the site from which it was collected, and 5) the
probable dispersal mechanism. This
collection will be due in your lab on Tuesday,
November or , Thursday
2 November 2000.
In lab we will discuss these mechanisms and go out into the field to look
at other examples of fruit dissemination mechanisms.