The Psilophytes - The Psilophytes The Division Psilophyta...

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The Psilophytes The Division Psilophyta consists of Psilotum nudum (the whisk fern, shown in Figure 11), a living plant that resembling what paleobotanists believe Cooksonia to have been: a naked, photosynthetic stem bearing sporangia. Also in the group is Tmesipteris , which resembles Psilotum except for its possession of smallo vascularized leaves arising on opposite sides of the stem. However, most paleobotanists doubt that Psilotum is a direct descendant of Cooksonia . Molecular studies suggest an affiliation with ferns for Psilotum. Psilotum also has three fused sporangia, termed a synangium, located on the sides of the stems (instead of the tips of stems as in Cooksonia ). The Lycophytes
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The next group, the Division Lycophyta, have their sporangia organized into strobili (singular: strobilus). A strobilus is a series of sporangia and modified leaves closely grouped on a stem tip. The leaves in strobili are soft and fleshy as opposed to the hard, modified leaves in cones. Leaves that contained vascular tissue are another major advance for this group. The
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The Psilophytes - The Psilophytes The Division Psilophyta...

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