Interesting Science Picture: Part III

Similarity of stress-treated, rolled marchantioid mats to Prototaxites . (A) Stress-treated and rolled marchantioid mat. Bar = 4 mm. (B) Crosscut roll, demonstrating the general appearance of concentric or eccentric rings and felted periphery. Bar = 1 mm. (C) SEM view of edge of a cross-cut roll, giving the appearance of concentric rings of tubes in diverse orientations separated by regions of resistant, nonrhizoid tissue. Bar = 100 μ m. (D) Crosssectioned roll, showing part of a ring of uncollapsed rhizoids occurring in diverse orientations. Bar = 100 μ m. (E) Prototaxites section showing open tubes of similar diverse orientation. Bar = 100 μ m.

From here