Darwin called the evolution of the Angiosperms a

“ Perplexing phenomenon”

…and in a letter to Joseph Hooker he called them an…

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www.jdhooker.org.uk

“Abominable Mystery”

—Charles Darwin in a letter to Sir Joseph Hooker, 1879.

Three Main Questions

1. Where did they come from?

2. How did they diversify so quickly?

3. How do they maintain high diversity?

Stamen series from leaf-like to a slender filament.

Lilium philadelphicum, Wood Lily, Liliaceae

Anthers with rust colored pollen

Narcissus pollen is typical monocot pollen (monosulcate)

Arabidopsis pollen is tricolpate (three long grooves) and is typical for a large number of dicots.

Helianthus (Asteraceae) pollen remf.dartmouth.edu/images/botanicalPollenSEM/image/10asteraceae(helian.)pollen.jpg&imgrefurl=http://remf.dartmouth.edu/images/botanicalPollenSEM

Ambrosia - Ragweed! Pollen

Oak Pollen- wind dispersed

Impatiens pollen is tetracolpate (with 4 slits). Note sculpting of exine, slits for pollen germination, and raphide crystals.

Cathy Small ‘09

Impatiens pallida

Sepal modified to be a nectar producing spur

Pollen

Raphide Crystals

Rhingia naisica eating pollen of Impatiens pallida

Pollen Tube

Stigmatic papillae

Pollen Grain -polyporate (with many round pores)

Sagina nodosa (Caryophyllaceae)

Pollen grains germinate to form the male gametophyte

1

2

Meiosis, 3 products Disintegrate leaving one megaspore

3

4

5

1st mitotic division

2nd mitotic Division

All megaspore images from: http://images.google.com/imgres?imgurl=www.botany.hawaii.edu/faculty/webb/BOT410/Angiosperm

3rd Mitotic Division

FemaleGametophyte (embryo sac)

Polar Nuclei