Book contents
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- 1 General features of the plant kingdom
- 2 The subkingdom Algae: Part 1
- 3 The subkingdom Algae: Part 2
- 4 The subkingdom Algae: Part 3
- 5 The subkingdom Embryophyta: division Bryophyta (mosses and liverworts)
- 6 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 1
- 7 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 2
- 8 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 3
- 9 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 4
- Glossary
- Suggestions for further reading
- Index
7 - The subkingdom Embryophyta (cont.): division Tracheophyta, Part 2
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- 1 General features of the plant kingdom
- 2 The subkingdom Algae: Part 1
- 3 The subkingdom Algae: Part 2
- 4 The subkingdom Algae: Part 3
- 5 The subkingdom Embryophyta: division Bryophyta (mosses and liverworts)
- 6 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 1
- 7 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 2
- 8 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 3
- 9 The subkingdom Embryophyta (cont.): division Tracheophyta, Part 4
- Glossary
- Suggestions for further reading
- Index
Summary
Polypodiopsida (ferns)
The class Polypodiopsida encompasses both wholly fossil and also living representatives, many of which have a long fossil history. The general features of the class can be summarized as follows:
Sporophyte herbaceous or arborescent, in many forms rhizomatous. Leaves often compound (megaphylls). Vascular system of tracheids and phloem, usually lacking clearly defined secondary tissue. Stele often divided into meristeles. Leaf traces often complex, leaving a parenchymatous gap in the stele at their origin. Sporangia borne on leaves, but never on the adaxial surface of a microphyll. Mostly homosporous; a few (living and fossil) heterosporous. Gametophytes (known only in living forms) simple, usually autotrophic, lacking vascular tissue. Archegoniate. Spermatozoids multiflagellate. Embryogeny typically endoscopic.
The living Polypodiopsida fall into six orders, namely the Marattiales, Ophioglossales, Psilotales, Osmundales, Polypodiales and Hydropteridales, referred to collectively as ferns. Of these, the first three orders are eusporangiate (p. 151), while the Polypodiales, and the Salviniales and Marsileales (p. 212) of the now validated Hydropteridales (p. 216), are leptosporangiate (p. 190). The Osmundales have in general leptosporangiate characteristics, but the sporangia develop in a manner recalling that of eusporangiate sporangia. The ferns are an important element of the world's flora, numbering about 10000 species and being particularly conspicuous in warm humid regions. They show the greatest range of growth forms amongst the vascular archegoniates. Although largely herbaceous, a number of ferns of the tropics and subtropics (mostly belonging to the family Cyatheaceae) achieve the form and stature of simple trees.
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- Information
- Green PlantsTheir Origin and Diversity, pp. 172 - 217Publisher: Cambridge University PressPrint publication year: 2000