Q. If intelligent extraterrestrials visited Earth 475 million years ago, and after that again 300 million years ago (at the close of the Carboniferous period), what trends would they have noticed in Earth's terrestrial vegetation over this period?

1. Trend from dominant gametophytes to dominant sporophytes

2. Trend from sporangia borne on modified leaves (sporophylls) to sporangia borne on stalks (seta)

3. Trend from no true leaves, to microphylls, to megaphylls

4. Trend from soil-surface-hugging plants to "overtopping" plants

5. Trend toward increased lignifications of conducting systems