6. Plant Systematics Laboratory #6

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Plant Systematics Laboratory #6

evolution of Flowering Plants

1. To be able to recognize and name (on sight) the major apomorphies of the angiosperms and evaluate their adaptive significance.

2. To be able to recognize and name (on sight) the major organs or structural components of these taxa, including knowing all terms listed in bold type.


Dissect a flower from the material available. Note the basic floral parts: a perianth, composed of a calyx of one or more sepals and a corolla or one or more petals; an androecium, composed of one or more stamens, each with an anther and filament, the latter of which may be absent; and a gynoecium composed of one or more pistils, each with an ovary, one or more styles (which may be absent) and one or more stigmas. Draw the whole flower and label the parts.

Observe the demonstration slide of early flower development in longitudinal-section. Note the resemblance between the determinate flower shoot and a vegetative shoot.

Observe the demonstration slide of a flower in cross-section. Draw, noting the perianth, stamens (with pollen inside), ovary, carpels, and ovules.


Remove a single anther from flowers of different stages (before and after pollen release) and observe under high magnification. Note the two anther halves, each half called a theca (plural, thecae). Section a very young anther or observe the microscope slides and note the two microsporangia per theca. Draw and label. At dehiscence these microsporangia fuse into a single anther locule.

Reduced Male Gametophyte

Observe an Angiosperm pollen grain from either a prepared slide or a wet mount (stained with acetocarmine or toluidine blue). Note the tube cell nucleus and generative cell (which later divides into two sperm cells). Draw and label.

Observe the prepared slides of Angiosperm pollen germination. Note the pollen tube, generative cell, and tube nucleus. In some, the generative cell may have divided to form the two sperm cells? Draw and label.

If material is available, observe the gynoecium of a species that is apocarpous (carpels unfused) and of a species that is syncarpous (carpels fused).

Draw and label the pistils of the apocarpous species (if available), showing ovary, style, and stigma.

Observe the prepared slide of a flower longitudinal-section. Note the basic parts of the flower. In the ovary, observe locule(s), ovules, and placentae. Draw and label the latter.

If available, observe stages of fruit development. Note how an ovary can drastically change shape and increase in size as it matures into a fruit. Draw. What is the adaptive significance of a fruit?
Reduced Female Gametophyte

Observe under the dissecting scope the ovary cross sections of Lilium or Fritillaria. Make an outline drawing, showing ovary wall, locules, and ovules. Note the two linear rows of ovules per carpel.

Observe Lilium or Fritillariaovules with a "compound" microscope. Observe a single ovule in mid-sagittal view, showing the funiculus, inner integument, outer integument, micropyle, and megasporangium (nucellus). Observe a mature female gametophyte of Lilium or Fritillaria, noting the three antipodal cells, two polar nuclei, and 3 cells of the "egg apparatus" (egg and 2 synergids). Draw and label.

If time permits, observe earlier developmental stages of Lilium or Fritillariaovule development.


Observe the demonstration of a prepared slide of an angiosperm seed (e. g., Capsella bursa-pastoris Shephard's Purse, Brassicaceae). Observe the endosperm encasing the embryo, both surrounded by a seed coat. Note the parts of the embryo: radical, hypocotyl, epicotyl, cotyledons. How many cotyledons are there? Draw and label.

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