Page:Popular Science Monthly Volume 77.djvu/339

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THE RELATION OF PALEOBOTANY TO PHYLOGENY

HE history of plant life has been the central idea in all botanical studies from the very earliest times, whether expressed in the imperfect methods of the early German and Dutch botanists who desired simply to establish natural affinities on the basis of external resemblances, or in the ambitions of Cæsalpino to arrive at a classification of plants which should satisfy the conditions of relationship through the structure of all parts, and especially of the reproductive organs. For nearly four hundred years the external organs have been employed as the chief basis of those numerous systems of classification which have appeared from time to time. The idea that the reproductive organs and the minute interior structure of plants were of primary importance as first advocated by Cæsalpino, was for a long time lost to view, although it reappeared now and then in the works of later writers. Eventually it gained recognition and became a factor of increasing importance, until the most advanced systems are now employed involve an acceptance of both the external parts and the internal anatomy as essential factors.

From the time of Malpighi and Grew, to Goeppert and Corda, our knowledge of the interior structure of plants made great and rapid progress, and was later applied successfully by various investigators in the direction of establishing relationships. To no one are we more fully indebted for an elaboration of this idea than Williamson, whose researches into the structure of fossil plants from the Coal Measures of Great Britain, during the latter part of the last century, laid the real foundation of modern paleobotany.

In so brief a treatment as that which is now employed, it is impossible to more than touch upon some of the salient features in the relations of paleobotany to the course of phylogeny, but it is, nevertheless, worth while to give special emphasis to the now well-recognized fact that a thorough knowledge of the interior structure of the plant, and especially of the stem, leads to a more comprehensive and exact acquaintance with relationships than that of any other part. This arises from the fact that the minute anatomical details have a greater degree of stability than any other portion of the body, doubtless due to the fact that in its adjustment to the land habit, the environmental influences