Please read and answer all five questions.
Please use your time effectively by reading the questions carefully, and answering only what is asked in each one. Note the marks for each one (total = 50) and budget your time accordingly.
1. (15 marks) Please read the following technical descriptions of genera 1-7 and prepare a labeled sketch to show the flower (or flowers, if unisexual) of each genus in longitudinal section. Use the back of the page if you need more space.
Genus 1. Evergreen shrub or small tree. Leaves alternate, petiolate, simple, at first spirally arranged, then becoming distichous. Secondary xylem lacking vessels. Inflorescences few-flowered axillary panicles. Dioecious. Flowers with bracteoles that grade into 5-8 spirally arranged, larger tepals. Male flowers with several stamens. Female flowers with several free pistils, each with a uniovulate ovary. Megagametophyte monosporic, 8-nucleate. Fruit a cluster of stalked drupes each containing a single seed with copious endosperm and a small embryo.
cf. Amborella (male flower)
Genus 2. Rhizomatous herb. Leaves basal, long petiolate, bilobed (so as to resemble the wings of a butterfly). Secondary xylem with simple perforate vessels. Flower solitary, sepals 5-9, early deciduous; petals 6 or 8; stamens 6 or 8; pistil solitary with one locule containing 20-40 ovules. Megagametophyte monosporic, 8 nucleate. Fruit a many-seeded follicle. Seeds with copious endosperm and a small embryo.
cf. Jeffersonia (Berberidaceae)
Photo © 2003 Royal Ontario Museum
Genus 3. Annual herb. Leaves opposite, simple. Secondary xylem with simple perforate vessels. Inflorescence cymose. Flowers with tubular calyx, 5-lobed; petals 5, free; stamens 10; pistil with three locules in ovary, and 3 (-5) styles. Megagametophyte monosporic, 8-nucleate. Fruit a capsule. Seeds small, lacking endosperm at maturity.
cf. Silene (Caryophyllaceae)
Photo © 2003 Royal Ontario Museum
Genus 4. Tree. Leaves spirally arranged, simple. Secondary xylem vessels with scalariform perforations. Flowers solitary, terminal on branches or their axillary short shoots. Tepals 9-21, stamens and pistils numerous, all three spirally arranged on an elongate receptacle. Ovaries each with 2 ovules in a single chamber, developing into thick-walled single-seeded follicles. Megagametophyte monosporic, 8-nucleate. Seeds with fleshy sarcotesta, copious endosperm, and minute embryo.
cf. Magnolia (Magnoliaceae)
Genus 5. Woody vine. Leaves alternate, simple. Secondary xylem vessels with simple perforations. Flowers solitary, in leaf axils, epigynous. Calyx lacking; corolla tubular; stamens 6; ovary with 6 chambers. Megagametophyte monosporic, 8-nucleate. Fruit a septicidal capsule. Seeds with abundant oily endosperm enclosing a minute but well-developed embryo.
cf. Aristolochia (Aristolochiaceae) - Allan Gardens
Genus 6. Rhizomatous herb. Leaves opposite. Secondary xylem vessels with simple perforations. Inflorescence terminal, consisting of 2 epigynous flowers with their ovaries united. Calyx reduced to 4 minute, pointed lobes; corolla long tubular, with 4 lobes; stamens 4, inserted on the inner surface of the corolla tube. Each ovary with 4 uniovulate chambers. Megagametophyte monosporic, 8-nucleate. Fruit a syncarpous berry-like drupe. Seeds with embryo surrounded by copious oily endosperm.
cf. Mitchella (Rubiaceae)
Photo © 2003 Royal Ontario Museum
Genus 7. Rhizomatous aquatic perennial. Floating leaves on long petioles, simple, spirally arranged on submerged rhizome. Secondary xylem vessels with simple perforations found only in the roots. Flowers solitary, from leaf sites. Sepals 4; petals 8-40, spirally arranged; stamens several hundred, spirally arranged; pistil with 8-35 multiovulate chambers. Megagametophyte tetrasporic, 4 nucleate. Fruit a many-seeded berry. Seeds lacking endosperm at maturity, the embryo small.
cf. Nymphaea (Nymphaeaceae)
2. (5 marks) Explain the descriptions of secondary xylem given for genera 1-7.
All seven genera are flowering plants, but genus 1 has wood resembling that of gymnosperms in that it consists exclusively of tracheids and fibers; vessels are completely lacking. Where vessels are present they vary with respect to perforation plate structure (scalariform - thought to be more primitive; e.g. Magnolia, below left - versus simple; e.g. Acer, below right).
3. (15 marks) Tabulate the information available for genera 1-7 so as to calculate an advancement index in the spirit of Bessey's dicta. In other words, use a-h below to describe the features you will analyze, indicating their primitive (0) and advanced (1) states, and then fill in the table accordingly .
Feature, states, and their scores (0/1):
a. Feature: evergreen (0) / deciduous (1)
b. Feature: woody (0) / herbaceous (1)
c. Feature: leaves opposite (0) / alternate (1)
d. Feature: flowers perfect (0) / unisexual (1)
e. Feature: floral parts many (0) / few (1 - for each of the perianth, androecium, and gynoecium separately; plus 1 if absent)
f. Feature: floral parts free (0) / joined (1 - for each of the perianth, androecium, and gynoecium separately)
g. Feature: hypogyny (0) / epigyny (1)
h. Feature: seeds with abundant endosperm, (small) embryo (0) / endosperm lacking at maturity (1)
other features were suggested, such as perforation plate scalariform versus
simple, or ovaries uni- versus multiovulate, but the justification or the
polarity was not given]
[scoring >1 floral part with respect to number and fusion (e, f) is obviously a short hand, and impacts on the number of comparisons to be used in the advancement index denominator; the principal concern here was whether you understood Bessy's dicta, and could apply them to the information provided]
4. (15 marks) Thorn trees and medlars - nomenclature problems.
Plants of the genera Crataegus and Mespilus, in the family Rosaceae, are small trees of Eurasia and America that are used medicinally and sometimes for food. The morphological characteristics that distinguish the medicinally important taxa may be difficult to observe and some nomenclatural confusion has resulted.
In framing your answers,
you should consider that all decisions and conditions from previous questions
remain in effect until they are explicitly changed.
The following taxa have been described and associated with the corresponding types:
|Crataegus L., 1753||[type C. oxyacantha L.]|
|Mespilus L., 1753||[type M. germanica L.]|
|Crataegus L. series Purpureofructi J.B.Phipps & O'Kennon, 1998||[type C. okanaganensis J. B. Phipps & O'Kennon]|
|Crataegus oxyacantha L. 1753||[type: specimen 'A']|
|Mespilus germanica L. 1753||[type: specimen 'B']|
|Mespilus cotoneaster L. 1753||[type: specimen 'C']|
|Mespilus laevigata Poiret 1798||[type: specimen 'D']|
|Crataegus curvisepala Lindm. 1918||[type: specimen 'E']|
|Mespilus canescens Phipps 1990||[type: specimen 'F']|
|Crataegus okanaganensis J. B. Phipps & O'Kennon 1998||[type: specimen 'G']|
In addition, the following
relevant combination has been published:
Crataegus laevigata (Poiret) DC. 1825
Solve the following problems:
a. If the medlars, specimens B and F, are best considered as two varieties of the same species, what are the correct variety names?
M. gemanica L. var. germanica [autonym]
L. var. canescens (Phipps) <student>
b. If specimens A, B, and C represent three different genera, what are the names of the genera?
L., Mespilus L., and "Your choice" <student>
c. What is the correct series name for the species that includes specimens A, D, and E?
L. series Crataegus [contains type of the genus]
d. If the okanagan hawthorn, specimen G, belongs to the same genus as the two-styled hawthorns (specimens A, D, and E) what are the correct names for these two species?
oxyacantha L. [or C. laevigata (Poiret)
e. Linnaeus made a mistake in his description of C. oxyacantha so that his type specimen 'A' does not match the description, although specimens 'D' and 'E' do match Linnaeus' description. The name C. oxyacantha is commonly applied to a very important medicinal plant and much confusion would result from an announcement that the name of this plant must be corrected. Can you think of an appropriate action by the International Botanical Congress that would minimize the confusion? Briefly explain why this action would be helpful.
Nadia and I both would make a proposal to reject C. oxyacantha as confusing, but I also accepted proposals to conserve this name.
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