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THE POPULAR SCIENCE MONTHLY.

surveys, wherever such co-operation will advance the work of the survey in accordance with its general scope and plans and will assist the local surveys.

The division of engraving and printing has been very successful in its work on the geologic folios; and it is hoped that arrangements can be perfected and authority secured for engraving and printing under its immediate direction all the maps of the survey.

Such special studies will be made in the chemical, paleontological, petrographical, and physical laboratories as may be needful to solve the problems that arise in connection with the areal geology or in the investigation of important scientific and economic problems.

The legislative branch of the Government has been very liberal in the past, and it is anticipated that the work will be fully sustained in the future. On the part of the survey it is proposed to retain the services of the most capable men that can be secured; to maintain the work at the highest standard of efficiency possible; and to advance it as rapidly as the means provided will permit.

THE THORNS OF PLANTS.
By M. HENRI COUPIN.

THE seeming absence of means of defense in plants, putting them in contrast—to the eye—with animals, which are bountifully and variously armed, is only apparent. A not very close examination of the behavior of plants toward animals, their great enemies, will soon satisfy one that they have many protective organs, some of them very efficacious. The spines, thorns, and prickles with which the stems and the leaves of some plants bristle are known to all, and we can hardly fail to perceive a protecting function in the aggressive defense of plants against animals and against the hand of man put forth to pluck them. In the spring, for instance, when vegetation is very little forward, the plum trees would soon disappear completely under the attacks of cattle, sheep, horses, and other foliage-loving animals, if Nature had not provided them with those long, sharp spines that make browsing of them very difficult if not impossible. The shapes of thorns are various, but may always be brought back to a protuberance broad at the base and pointed at its free end, and of an extremely hard consistence. Usually simple, they are sometimes bifid or trifid. Their positions are various. All the organs of plants may be said to bear them: the stem, as in the rose; the base of the leaves, as in the barberry; the leaves, as in the thistle;