Figure 18.7   Early vascular plants. (ad) The oldest land plant, Cooksonia from the Silurian to Early Devonian. Early Devonian examples from Wales, showing a complete sporangium at the end of a short stalk (a), a stoma (b) and spores (c). The sporangium is 1.6 mm wide, the stoma is 40 m wide and the spores are 35 m in diameter. (d) Reconstruction of Cooksonia caledonica, a Late Silurian form, about 60 mm tall. (e) Zosterophyllum, a zosterophyllopsid from the Early Devonian of Germany, 150 mm tall. (ad, courtesy of Dianne Edwards; e, based on Thomas & Spicer 1987.)

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