Page:Popular Science Monthly Volume 67.djvu/471

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HE big trees, or sequoias, have furnished a theme for song and story and have been a Mecca for the tourist for so long a time that any remarks regarding the size or longevity of the far-famed trees of Mariposa and Calaveras would seem trite. Their present isolation—for they are but few in number and do not seem to be holding their own in the struggle with the surrounding vegetation or with the cupidity of civilization—but adds to their majestic grandeur.

To the traveler who journeys to California and for the first time stands in their mighty presence many questions may suggest themselves. How long has it taken these giants of the forest to reach up some four hundred feet above mother earth? Were they created thus? Were they just entering upon a career before the red man's fire or the pale-face's ax checked them, or are they the survivors of a long existing line, struggling to maintain themselves in their last stronghold?

The records of their descent are locked up in the rocks and clays of the world, bits of twigs, cones, and occasionally large pieces of trunks that floated down to the ancient seas and were entombed in the sand and mud, to become preserved as fossils for the edification of later ages. Exploration has unearthed a part of this record. Sequoia remains have been found at almost every locality where Mesozoic fossil plants have been discovered; the cones, especially, because of their hard woody structure, being admirably adapted for preservation. In fact the fossil cones were described away back in the first quarter of the nineteenth century, even before the big trees of California had been described.

So we learn that death has played sad havoc in their noble line. Some have been dead, say, seven million years, with thousands of feet of rock lying vertically over their graves. Fig. 1 gives a diagrammatical summary of sequoia evolution, with the accompanying changes in geological, climatic and floral conditions. The left-hand column shows an ideal geological section, with the ages and periods, and their probable durations expressed roughly in years. In the middle column the procession of changing physical conditions are shown, together with the accompanying changes in climate and flora. The right-hand column is devoted exclusively to events in the genealogy of the sequoia.

The earliest known species is represented by well-defined cones