Questions for Further Thought

1. In our discussion of Asteroxylon, we suggested that the differentiation of a vascular strand that extends toward the enations may be related to the development of the enation itself rather than a functional/adaptive consequence of photosynthetic activity in the enation. How might you test this pair of hypotheses?
2. List features shared in common between the seed plant clade and arborescent lycopsids. Note whether each is a shared ancestral, or convergent feature.
3. Note the distinction between structures showing convergence (ignore the plesiomorphic traits) for functional reasons and those showing convergence simply because similar anatomical building blocks are being used. What does such obvious convergence, despite the different origins of structures, imply about evolutionary "choices" or "options" available to plants when faced with the problems of terrestrial life?
4. Arborescent lycopsids are extinct today and the clade is represented by only a handful of herbaceous species. Would you say that this clade is an evolutionary failure? Explain.

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