has a curious cross-shaped mark on its base, the stems of stigmaria strike out horizontally, first as four great roots which subdivide as they proceed. Their subdivisions are dichotomous, each root splitting equally into two, and thus they want that intricate interlacing of rootlet which is so familiar to us. The whole disposition of these under-ground stems is singularly straight and regular, leading us to believe that they shot out freely through a soft muddy soil. [Footnote 21: Such is the usual aspect of the plant. But as the stems have been, for the most part, greatly flattened by the pressure of the superincumbent rocks, the sharpness of the pattern has been much effaced. In some specimens described by Dr. Hooker, as having been found in an upright position, the external ornamentation presents an appearance somewhat different. What in the common specimens stand out as tubercules, are there seen to be deep circular cavities, in which the shrunk flagon-shaped bases of the rootlets are still observable. (See above, Fig. 13 _b_, which is taken from one of Dr. Hooker's plates. For a detailed description of the structure of stigmaria, see the paper above referred to in the _Geological Survey Memoirs_.) A very ornate species is mentioned by the late Hugh Miller, in which each tubercule formed the centre of a sculptured star, and the whole stem seemed covered over with flowers of the composite order. And what is, perhaps, still more curious, the stem was seen to end off 7 in an obtuse point, tuberculed like the rest of the plant.--_Testimony of the Rocks_, p. 461.]