IB Biology / Inglemoor HS
NAME: ______________________________________
Dissection of a Flower (Snapdragon: Antirrhinum
majus)
Directions: This handout consists of instructions, questions, and figures to guide
you. Enjoy! Your materials: fresh snapdragon flowers, forceps, pointers, sharp razor
blade, magnifying glass and/or dissecting microscope.
The flower cluster of a snapdragon consists of a central peduncle with
individual flowers along its side. The stalks of the individual flowers
are called pedicels. Remove a single flower from your table's
peduncle so that you obtain the pedicel and the bract, a small leaf-like
structure immediately below the pedicel.
1. Color figure 1(a) so that it resembles your flower.
2. Note the calyx at the base of the flower. It consists of ____ (how many?) green sepals. The
calyx encloses the young flower bud. In dicots, the sepals are usually green. In monocots
they are more likely to be colored.
3. The showy white or pigmented portion of the flower is the corolla. The corolla is
bilaterally symmetrical in the snapdragon. Name a flower that is radially symmetrical:
____________________________________ .
4. The snapdragon corolla is two-lipped. Unlike flowers with free or separate petals, the
snapdragon has fused petals. Inspect closely. The upper lip consists of ____ (how many?)
fused petals, while the lower lip consists of ____ (how many?) fused petals.
Pull down the lower lip of the corolla. This is what happens when a bumblebee lands on this
part of the flower. Note the structures closely pressed against the inner portion of the upper
lip.
5. Color figure 1(b) so that it resembles your flower.
6. The "male" portion of the flower consists of structures called stamens. Each stamen
consists of a slender stalk, the filament, and a terminal yellow anther. How many stamens
do you count in a snapdragon flower? _____
7. The anther consists of two pollen sacs in which pollen grains are produced. What part of
the bee brushes against the anthers as it searches for nectar? _______________
8. Transfer a few pollen grains to a microscope slide and make a wet mount. Examine with
the compound microscope. Describe the shapes of the pollen grains:
________________________________________________________________________
________________________________________________________________________
The "female" part of the flower consists of the carpel. The slender stalk-like portion of the
carpel is the style; the terminal, rough disc that is turned downward is the stigma. (Note the
position of this latter structure and recall the pollen grains on the back of the bumblebee!)
9. Pull the corolla away from its point of attachment inside the calyx. Do this by holding the
calyx in one hand, and gently pulling on the corolla with the other. Where are the
stamens attached? ________________________________________________________ .
10. The parts of the flower that remain after removing the corolla and stamens are the calyx
and carpel. Carefully remove the calyx by stripping off each of the sepals downward. This
carpel consists of three portions. The rough, usually sticky surface upon which the pollen
grains germinate is the _________________ . The slender stalk is the _______________________.
The basal, enlarged portion is the ____________________.
11. With a sharp razor blade, make a cross section through
the ovary of an older blossom, near its broadest part.
Examine the cut surface with a magnifying glass or
stereoscope. Each of the numerous white oval
structures is an ____________. Sketch & label the
cut surface of the ovary in the field of view at the
right.
Mag. ____ X
12. The ovary contains _____ (how many?) cavities. The number of cavities indicates the
number of units of which the carpel is composed.
Each pollen tube grows downward through the style and into an ovule, after which
fertilization occurs. Following fertilization, an embryo develops and the ovule ripens into a
seed. As ovules develop into seeds, the wall of the ovary enlarges and develops into the fruit.
13. Distinguish between pollination and fertilization:
___________________________________________________________________________
14. Judging from the their morphology, do you think snapdragon flowers tend to be selfpollinated or cross-pollinated? Explain.
___________________________________________________________________________
Great snapdragon photos on the Web:
www.biologie.uni-hamburg.de/b-online/library/snapdragon/flower.html
www.maltawildplants.com/SCRO/Antirrhinum_tortuosum.php