Supergroup Archaeplastida II – seed plants – Lab Exercises

Please choose one prepared slide to image. Take a picture under the microscope and submit via Canvas. Make sure that your picture is appropriately centered, cropped, and focused. Add a scale bar.

I. Non-flowering Seed Plants (Gymnosperms)

Pinophyta (Conifers)

Exercise 1.1: Examine the available specimens of conifers.  

Examine the available conifer living and preserved specimens.  Note the needle-like or scale–like leaves.  The small leaf surface area and thick waxy cuticle of these leaves helps reduce water loss during hot dry summers or winters when soil water is frozen.  Although conifer leaves may initially look similar, some are distinctive:

  • pines: needles are in “fascicles” of 2, 3, or more
  • spruces: needles are solitary, stiff, and sharply pointed.  A small woody peg remains on the stem when a leaf is shed
  • firs and Douglas firs: needles are solitary, flexible, and rounded at the tip.  Needles leave a smooth stem when shed
  • junipers: scale-like leaves are tiny and overlapping like the shingles on a roof

Also note the ovulate cones.  Conifers are monoecious with the ovulate cones persisting on individuals for years.  Ovulate cones are morphologically distinctive and are useful in identifying different conifer genera:

  • pines: small to large cones with thick woody cone scales borne around the cone axis
  • spruces: small to medium cones with papery and blunt-tipped scales 
  • firs: cone scales are shed as they mature, leaving the cone axis standing upright on the stem 
  • Douglas firs: cone scales are similar to those of spruces, but slightly woodier.  Each cone scale is “subtended” by a papery bract which has three-toothed apex
  • junipers: cones form a “berry” by the fusion of several fleshy cone scales

Choose one conifer and sketch a few leaves and a cone.

Exercise 1.2: Examine a prepared slide of a pine microsporangiate (staminate) cone.  

Observe a microsporophyll with a microsporangium containing pollen.  Draw one microsporophyll.

Exercise 1.3: Examine a prepared slide of a pine ovulate cone with ovules on megasporophylls.  

Observe a pine ovule including: integument, female gametophyte, archegonium with neck cells, and egg cell.  Draw a pine ovule.

Cycadophyta (Cycads)

Exercise 2.1: Examine the available specimens of living cycads.  

Examine the available cycads.  Note the large, pinnately compound (palm-like) leaves borne in a crown at the stem apex.  Cycads stems are “woody,” but sparingly so.  Most of their width comes from persistent leaf bases.  Note the cones on the specimens of Zamia.  These plants are dioecious.  Can you distinguish between the microsporangiate and ovulate cones?  Sketch a cycad and a cone.

Ginkgophyta (Ginkgoes)

Exercise 3: Examine the available specimen of Ginkgo biloba.  

Examine the herbarium sheet of Ginkgo biloba.  Note the distinctive wedge-shaped leaves with open dichotomous venation.  Ginkgo trees are deciduous and are similar to flowering plant trees in overall appearance.  Note the microsporangiate cones on the specimen sheet.  They are ephemeral and dropped by the plant soon after pollen release.  Ovules are borne in pairs at the tips of forked stems called sporangiophores.  Ginkgoes are dioecious.  Most commonly planted ginkgo varieties are microsporangiate (sold as “males”).  Ovulate individuals generally are unpopular because the outer seed coat layer (sarcotesta) is fleshy and contains butyric acid, a volatile organic acid that gives vomit its distinctive odor.   Sketch a leaf, microsporangiate cone, and sporangiophore with ovules.

Gnetophyta (Gnetophytes)

Exercise 4: Examine the available specimens of gnetophytes.  

Examine the herbarium sheets of Ephedra.  This is a common shrub (with three common species) in southern Utah.  The cylindrical stems are green and photosynthetic.  The tiny leaves are non-photosynthetic scales.  These plants are dioecious, forming small microsporangiate and ovulate cones.

Locally these shrubs are called Mormon tea or Brigham tea (a reference to them being used to make a rather astringent hot beverage) and are more broadly called joint firs.   Sketch a small portion of a plant.  Also sketch a microsporangiate and an ovulate cone.

II. Flowering Plants (Angiosperms)

Magnoliophyta (Flowering Plants)

Exercise 5.1: Examine a prepared slide of a Lilium (Lily) anther with tetrads. 

Observe an anther containing tetrads of microspores.  Draw a tetrad.

Exercise 5.2: Examine a prepared slide of a Lilium mature anther.  

Observe the mature pollen grains within the anther.  Find a pollen grain that shows a small generative cell and a larger tube nucleus.  Draw a two-celled pollen grain.

Exercise 5.3: Examine a prepared slide of a Lilium ovary with megaspore mother cells.  

Observe the cross sections through a lily ovary.  Notice the three chambers (locules), each of which contains two ovules.  Closely examine an ovule.  Observe the integuments, micropyle (opening through the integuments), and microspore mother cell (note: to see these will require a medial section through an ovule – there are many ovules on each slide, so look around until you find a good one).  Draw one ovule showing these features.

Exercise 5.4: Examine the demonstration of a Lilium mature megagametophyte (“embryo sac”).  

Observe the longitudinal view through a lily megagametophyte.  Lily has Fritillaria-type development.  Observe the antipodal cells, polar nuclei, synergid cells, and egg cell (remember that the egg cell will be closest to the micropyle).  Can you see a difference in size between the triploid and haploid nuclei?  Draw the ovule, including the megagametophyte.  Note: please do not move the view.  You may adjust the focus, but please be careful with this slide.

Exercise 5.5: Examine the prepared slide or fresh material of a seed.  

Observe the seed coat and embryonic sporophyte.  The sporophyte will have one or two embryonic leaves (cotyledons) and an embryonic stem.  Draw an embryo.

 Floral Structure and Variation

Exercise 5.6: Observe the model of a generalized flower.  

Use this model to identify the sepals, petals, stamens (filaments and anthers) and pistils (stigma, style, and ovary).  Note the “cut-away” of the ovary depicting an ovule with a mature megagametophyte within the locule.  Trace the route of the pollen tube to the micropyle and note the progression of the sperm towards the ovule.

Exercise 5.7: Observe the available flowers.  

In each case try to identify the four types of floral appendages.  Try to find examples of the following types of floral variation: symmetry, fusion, number of floral appendages/series, and ovary position.  Use your observations to fill in the following table for at least one flower: 

Flower Type (if known):

                                                                                          Sepals                       Petals                        Stamens_                Pistils

Number of:

Fusion (yes/no):

Symmetry (radial/bilateral):

Ovary Position (superior/inferior):

Number of Carpels:

Exercise 5.8: Dissect the ovary of a flower.  

Observe the locules and ovules. How many carpels make up this pistil?  These features are summarized below:

  1. Locules – Chamber(s) within the ovary that contain the ovules.  The number of locules is generally related to the number of carpels which form the pistil.
  2. Ovules – Ovules are small, spherical to oblong structures attached to the ovary wall by a short stalk.  Each contains an embryo sac (including an egg cell) and will develop into a seed following fertilization.

                  3.   Carpels – Carpels are the floral appendages from which the pistil is formed.  The number of 

carpels is often indicated by the number of locules, the arrangement of ovules, lobation, and 

sutures (visible as grooves on the outside of the ovary).

Draw an ovary in cross (and/or) longitudinal section.  Note as many of these features as you can.


Exercise 5.9: Observe the available fruit types.  

Use information from dissection and observation to identify fruit types.  Include five of these in the table below:

        Fruit Name (if known)                    Description                                                  Fruit Type