signatures supposed that the color and form of plants indicated their relations, good or evil, to the human race, in reference to which they were especially created. This crude superstition attained greatest favor in the sixteenth century, and is still prevalent in obscure form among the lower classes in certain portions of Europe. The use of colors as a distinguishing mark between species, families, and groups began quite early in the history of attempts at classification, and still forms a minor character in modern systems. A wholly new point of view was that taken by Konrad Sprengel, in his history of the biological significance of color (Das entdeckte Geheimniss der Natur im Bau und Befruchtung der Blumen; Berlin, 1793). To Sprengel is due the idea that the colors of the secondary reproductive organs are a device for the attraction of insects, thus securing cross-fertilization. Investigations in many directions from this idea have revealed the fact that plants in a similar manner attract insects and other animals for many other purposes besides fertilization, and in some instances avoid such visitors, for various reasons connected with their development, in a similar manner. Such an amount of attention has been given to these ecologic color adaptations that the aggregate mass of the results recorded is nothing short of colossal. That these results are of immense value and importance goes without saying: yet, given such a thesis, it is impossible that the observations of both trained and amateur workers should not contain a large number of misinterpreted facts. The general principle has been drawn upon to furnish solutions to complicated or unusual arrangements of color, in a manner highly improbable and unscientific and in many instances verging upon the impossible and ridiculous. That it can not be assumed a priori that the colors exhibited by the flowers or any other organs of the plant are devices to attract and guide insect visitors is becoming more and more apparent. Timely attention has been called to the perversion of this principle by the writer of a recent article on floral biology (Willis, Science Progress, No. 21, 1895). That great care is necessary in the interpretation of areas of color in plants is emphasized by the fact that accumulating observations tend to show that a color sense is wholly lacking except among the higher insects, and that if the colors of flowers were fashioned to attract insect visitors the directive impulse must have been received at a very recent date—that is, since the acquisition of the color sense by insects. It is by no means the purpose of this article to discredit the great mass of well-confirmed facts concerning the uses of the colors as an adaptation to insect visitors, but chiefly to call attention to conclusions afforded by the last fifteen years of research upon the formation and physiological uses of color in plants. The functions sub-
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POPULAR SCIENCE MONTHLY.