Week 3 Laboratory

Flowers, Inflorescences, Fruits

<Lab Schedule> <Next Lab>

I. Minilecture [pdf version] on inflorescence types: know the difference between determinate and indeterminate inflorescences. Be able to identify (1) indeterminate types: raceme, panicle, umbel, spike, corymb, head or composite; (2) determinate types: dichasium, cyme or compound dichasium, monochasium; and (3) ament/catkin and spathe/spadix. See pp. 484-489 in Plant Systematics, 2nd ed., Chpt 9.


II. Floral dissections: dissect the flower of each of the first three species and the fourth as you have time. Work in pairs or small groups but be sure each member has the opportunity to see all the parts and the modifications. Take out your dissecting microscope and identify all portions of the flower using lecture notes and handouts as a guide; draw longitudinal diagrams of the flowers in your lab notebook and indicate the different floral parts; draw cross sections of the ovary in your lab notebook and indicate the type of ovary (number of carpels, placentation, superior or inferior, etc.); notice and record modifications of the flowers (asymmetry, fusion, adnation, reduction, etc.). Refer to Chapter 9 in Plant Systematics, 2nd ed., pages 468-484, or pages 19-25 in the Zomlefer resource for more information and illustrations. Illustrations are provided here for review for basic floral parts, the carpel as a modified leaf, distinction between carpel and pistil using the origin of the multi-carpellate pistil, differences of ovary position, and various placentation types. See also lecture notes and handouts.

  A. Nicotiana alata (tobacco, Solanaceae): see pp. 416-417 [T], 213-215 [Z]

  B. Sedum sp. (sedum, Crassulaceae): see pp. 287-289 [T], not in Zomlefer

  C. Fuchsia spp. (fuchsia, Onagraceae): see pp. 353-356 [T], 229-231 [Z]


III. Floral formulas: when you have had an opportunity to look at most of the flowers in some detail, your instructor will discuss the use of floral formulas as a shorthand notation to describe the variation in these flowers (see handout following "Angiosperm Morphology" lecture outline in course booklet). Try to fill out the floral formula – on the next page - for each of the plants you dissected. This kind of floral formula will be provided to you in lecture as we go through the major groups of flowering plants. See pages 184-185 in Plant Systematics, 2nd ed., for more information on floral formulas.


IV. Floral variation demonstrations: around the room are placed a number of flowering plants that show specific or unusual examples of floral evolution. Study these examples looking especially for various kinds of fusion, change in floral symmetry, position of gynoecium, and specialized floral parts. You do not have to memorize the plants, but you should be familiar with the kind of floral variation that is demonstrated with the plants.


V. Fruit types to examine on table in laboratory (see lab handout on Key to Fruits). You do not need to memorize these fruit types, as they will be covered later individually during lectures and laboratories. However, you should know and understand Simple, Aggregate, and Multiple fruits, and Dehiscent Dry, Indehiscent Dry, and Fleshy fruits. Examine the demonstration the demonstration of fruit types using the Key to Fruits and enjoy the fruits as you do so. See pp. 489-493 in Plant Systematics, 2nd ed.


VI. Review of floral parts, fruits, and inflorescences - see the Plant Systematics website at Texas A&M.