tree-logo.gif (7741 bytes) Plant Taxonomy (BIOL308)  -  Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe/

Floral Morphology Exercises

General Procedure:
    Obtain a plant with flowers.  Observe the type of inflorescence and whether or not bracts are associated with the inflorescence and/or individual flowers. Remove a single flower from the inflorescence and then, on a separate sheet of paper, sketch the flower as you carefully dissect it. Lay the parts on a note card (i.e., 4 x 6) and when you are finished studying the parts, tape them to the card with clear cellophane tape or contact paper for future reference (like a mini-herbarium specimen). Answer the questions listed below. Some good specimens to use include Sedum, Nicotiana (flowering tobacco) or Petunia, Linaria vulgaris (Butter and eggs), and Lotus corniculatus (Bird's foot trefoil).

A. General Features:

  1. What type of inflorescence does this plant have?
  2. Are bracts associated with the flowers/inflorescence?
  3. Is the flower complete or incomplete?
  4. If incomplete, which set of floral organs is missing?
  5. Is the flower perfect or imperfect?
  6. If imperfect, is it monoecious or dioecious (or other)?
  7. Is the flower regular (actinomorphic) or irregular (zygomorphic)?

B. Calyx:

  1. How many sepals are present?
  2. Are the sepals distinct or connate?

C. Corolla:

  1. How many petals are present?
  2. Are they distinct or connate?

D. Androecium:

  1. How many stamens are present?
  2. Are they distinct or connate?
  3. Are the stamens free or epipetalous (adnate to the calyx)?

E. Gynoecium:

  1. How many carpels?
  2. How many styles?
  3. How many stigmas?
  4. What is your evidence for carpel number?
  5. Is the gynoecium unicarpellate, apocarpous, or syncarpous?
  6. What is the position of the ovary (superior/inferior)?
  7. Is the insertion hypogynous, epigynous or perigynous
  8. Approximately how many ovules are in each ovary?

F. Taxonomy:

  1. Write a floral formula for the flower
  2. Identify the family to which this plant belongs
  3. Write the scientific name for this plant
  4. List, in order, the steps in a dichotomous key, such as Gleason & Cronquist, that identify the family to which this plant belongs.


II. Sunflowers: Plants in the sunflower family (Asteraceae) have rather unique floral structures. The inflorescence, which is called a head (or capitulum), is comprised of numerous individual flowers attached to a common receptacle and subtended by a cluster of bracts called an involucre. The head may be comprised of a combination of disk and/or ray flowers.

A. General:

  1. Looking down on the inflorescence, sketch the general appearance and distribution of the disk and ray flowers. Label the disk and ray flowers.
  2. Now, with a razor blade, cut down through the center of the flower and sketch a long section of the head. Label bracts (involucre), peduncle, disk flowers, ray flowers.
  3. Bracts (called chaff) are often found within the head attached to the receptacle. Is chaff present? ________ If so, remove one and sketch.

B.  Disk Flowers (if present): Remove a single disk flower and then sketch it. Label ovary, pappus (calyx), corolla, style, stigmas, androecium.

  1. Is this flower complete or incomplete?
  2. If incomplete, which set of floral organs is missing?
  3. Is the flower perfect or imperfect?
  4. If imperfect, is it monoecious or dioecious (or other)?
  5. Is the flower regular (actinomorphic) or irregular (zygomorphic)?
  6. Describe the pappus
  7. How many petals are present?
  8. Are they distinct or connate?
  9. How many stamens are present?
  10. Are the anthers distinct or connate?
  11. Are the stamens free or epipetalous (adnate to the calyx)?
  12. The anthers in this family often have terminal or basal appendages. Do you observe either? If so, describe them.
  13. How many carpels?
  14. How many styles?
  15. How many stigmas?
  16. What is your evidence for carpel number?
  17. Is the gynoecium unicarpellate, apocarpous, or syncarpous?
  18. What is the position of the ovary (superior/inferior)?
  19. Is the insertion hypogynous, epigynous or perigynous?
  20. Write a floral formula for this flower:

C.  Ray Flower (if present): Remove a single ray flower. Then, sketch and label.

  1. Is this flower complete or incomplete?
  2. If incomplete, which set of floral organs is missing?
  3. Is the flower perfect or imperfect?
  4. If imperfect, is it monoecious or dioecious (or other)?
  5. Is the flower regular (actinomorphic) or irregular (zygomorphic)?
  6. Describe the pappus
  7. How many petals are present?
  8. Are they distinct or connate?
  9. How many stamens are present?
  10. Are the anthers distinct or connate?
  11. Are the stamens free or epipetalous (adnate to the calyx)?
  12. The anthers in this family often have terminal or basal appendages. Do you observe either? If so, describe them.
  13. How many carpels?
  14. How many styles?
  15. How many stigmas?
  16. What is your evidence for carpel number?
  17. Is the gynoecium unicarpellate, apocarpous, or syncarpous?
  18. What is the position of the ovary (superior/inferior)?
  19. Is the insertion hypogynous, epigynous or perigynous?
  20. Write a floral formula for this flower:

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Last updated:  08/20/2007 / � Copyright by SG Saupe