Flower Dissection
Name____________________________ Date________
Flowers are more than ornamental parts of a plant. They are the reproductive structures of angiosperms,
or flowering plants. Flowers are structures for sexual reproduction. Thus, angiosperms are widespread.
Part A: External Anatomy of a Flower
Flowers have a variety of different sizes, shapes, and numbers of parts. The various parts of the flower
help with the transfer of the pollen to the egg. There are typically four rings of structures in flowers,
from outside to inside they are:
sepals
petals
stamens
carpels
Figure 1: Cross-section of an angiosperm
Sepals are green, leaf-like parts at the base of the flower. Some sepals are joined so it may be difficult
to see each one. Sepals protect the young flower.
Petals compose the next "ring" of flower structures. You can think of petals as modified leaves.
Examine the texture and color of the petals using a magnifying glass. If your flower is colored, pinch a
small piece of a petal between your fingers and examine the colorful pigment released. Petals may be
fused together making it difficult to count these numbers. If they are not fused, count the number of
petals. Petals protect the flower parts inside and their colors may attract insects.
To Do: Obtain a flower and examine it, using the diagram in Figure 1 as a reference. Identify the
sepals and petals. Remove the petals of your flower by gently pulling them off. This will reveal the
carpal and stamens.
1. How many petals does your flower have?
2. Why do you suppose the petals of flowers are so colorful, fragrant, uniquely shaped?
Part B: Monocots vs. Dicots
There are two classes of angiosperms: the monocots and the dicots. Analyze the diagrams below to
summarize the differences between monocots and dicots.
Figure 2: Comparison of Monocots and Dicots
3. a-g Create 2 columns in your lab notebook to answer a-g for Monocot and Dicot
Monocot Plants
Dicot Plants
a. Number of cotyledons in seeds
b. Number of sepals
c. Number of petals
d. Number of stamens
e. Sepals, Petals, Stamens in
multiples of 3, 4, or 5
f. Leaf veination: Parallel or Netlike?
g. Vascular tissue: Arranged in
bundles or arranged radially?
4. Is the flower you’re examining a monocot or dicot? ________________________________
4a. Justify your answer.
Part C: Reproductive Structures
Stamens are the male reproductive structures of the flower. They may be T-shaped, colored, straight or
gently curved. They consist of an anther supported by filament shaft. Pollen grains are released from
the anther. Each stamen will produce hundreds of pollen grains. Contained inside of each pollen grain
there are two sperm nuclei.
To Do: Carefully pull back the petals of the flower to expose the stamens. If necessary, use a razor
blade or scalpel to help expose the internal structures.
5. How many stamens do you see in your flower? _______
To Do: Examine the anther using a magnifying glass and touch the tip of your finger to the anther.
6. Did any pollen rub off on your finger? _______
To Do: Prepare a wet mount of pollen grains. Place an anther onto a slide and add a drop of water.
Cut the anther into several small pieces with the razor blade. Caution: Blade is sharp! Cut away
from your fingers! Add a coverslip and gently press down to squash the anther pieces. Examine the
anther pieces under low and high power.
7. Draw what you see in your lab notebook:
7a. Estimate how many pollen grains are present on each anther. ___________
Carpels are the female reproductive structures of the flower. The carpel encloses the egg cell and is
typically divided into the ovary, style, and stigma. A flower may have one or more carpels, either single
or fused. (A single carpel or a group of fused carpels is also known as a pistil.)
To Do: To see the carpel clearly, gently separate the flower from the green sepals and base. The
stamens will usually stay with the flower petals and the carpel remains attached to the base. This
separation occurs naturally when a tree or plant sheds its flowers.
Figure 3: A carpel
8. Does your flower have a single or fused carpel?_______
9. Why do you think the stigma is sticky?
To Do: Cut open the carpel to see the ovary. The ovary contains the haploid eggs.
You should see two sections to the ovary: the outer ovary walls and the ovules within. The ovules
contain one egg cell each. A placenta, a tiny stalk which connects each ovule to the ovary, may also be
visible.
10. Make a drawing of your ovary longitudinal section. Label its parts, including the ovary,
placenta, and ovule.
11. Estimate how many ovules are present within your flower. _____________________
12. What do the pollen grains and ovules have in common?
13. Compare the number of pollen grains in each flower with the number of ovules. Why
do you think there is a difference?
If a flower contains both male and female parts, botanists call them perfect flowers. Most flowers
(roughly 85%) are perfect flowers and are able to self-fertilize. Imperfect flowers contain either male or
female parts, but not both, and therefore, cannot self-fertilize.
14. Is the flower you examined perfect or imperfect?
Part D: Review
15. a- j. Summarize what you’ve learned by labeling the diagram below and filling out the table.
D
E
B
A
F
H
C
G
I
Functions and Sexual Associations
of Flower Parts
Part
A
B
C
D
E
F
G
H
I
J
Function
Male, Female,
or Neither
Pollen
Grains
Part E: Life Cycle of a Plant
16. Study the diagram below, then explain what is occurring at each numbered step.
17. Pollination is the process where pollen from the anther of one flower is transferred to
the stigma of another flower. List several ways that pollination can occur.
18. What is the difference between pollination and fertilization?
19. What do you think would happen if each of the following occurred? Relate your
answer to the next logical event in the sequence.
a. Pollen does not land on the top of the pistil.
b. A pollen tube does not grow down the neck of the pistil.
c. The sperm nucleus didn’t enter the ovule.
d. Insecticides were used on the flower and no insects were found.
Part F: Identification:
Identify each of the following as a monocot or a dicot. Explain your reasoning.
20. Station 1 ________________________________
21. Station 2 ________________________________
22. Station 3 ________________________________
23. Station 4 ________________________________
24. Station 5 ________________________________
25. Station 6 ________________________________
26. Station 7 ________________________________
27. Station 8 ________________________________
28. Station 9 ________________________________
29. Station 10 ________________________________