Page:Popular Science Monthly Volume 32.djvu/815

 to the animal kingdom. There can be no question that some of these are truly marine plants; and that plants of this kind occur in formations older than those in which we first find land-plants, and that they have continued to inhabit the sea down to the present time. It is also true that the oldest of these algæ closely resemble in form plants of this kind still existing; and, since their simple cellular structures and soft tissues are scarcely ever preserved, their general forms are all that we can know, so that their exact resemblance to or difference from modern types can rarely be determined. For the same reasons it has proved difficult clearly to distinguish them from mere inorganic markings or the traces of animals, and the greatest divergence of opinion has occurred in recent times on these subjects. The author of this work has given much attention to these remains, and has not been disposed to claim for the vegetable kingdom so many of them as some of his contemporaries. I believe there are many real examples of fossil algæ, but the difficulty is to distinguish them.

The genus Buthotrephis of Hall, which is characterized as having stems, subcylindric or compressed, with numerous branches, which are divaricating and sometimes leaf-like, contains some true algæ. A beautiful species, collected by Colonel Grant, of Hamilton, and now in the McGill College collection, may be described as follows:

Butthotrephis Grantii, S. N. (Fig. 5).—Stems and fronds smooth and slightly striate longitudinally, with curved and interrupted stride. Stem thick, bifurcating, the divisions terminating in irregularly pinnate fronds, apparently truncate at the extremities. The quantity of carbonaceous matter present would indicate thick, though perhaps flattened, stems and dense fleshy fronds.

It may be well to mention the remarkable Cauda-Galli fucoids, referred by Hall to the genus Spirophyton, and which are