THE NATURE AND ORIGIN OF STIPULES.
The investigation which has resulted in the preparation of this dissertation was undertaken with a view to determine the true nature and phylogenetic origin of those appendages of the bases of the petioles of leaves which are known as stipules and which are present in so large a number of the families of flowering plants.
The data have been collected from every available source ; the evidences to be gathered from known geological facts have been taken into consideration, observations have been made upon the morphology and anatomy of the foliar organs in a large number of cases, and the gradual modification of leaf-forms in the annual growth of plants from simple scales to adult leaves has been care fully studied. In addition to the data so gathered, the literature dealing with the subject, relatively scanty though it is, has yielded much valuable material both by the record given of the observa tions of others and by the suggestion of lines of investigation.
With all this material in hand, I have endeavored to ground the theoretical consideration of the problem upon the broadest founda tion possible in the present stage of the progress of science, and from a comparative study of the evidence gathered from all the various sources of information, have drawn the conclusions set forth at the close of my paper.
The results of my investigations arc herewith given to the pub lic with the conviction that conclusions arrived at in the manner indicated cannot fail of interest to the reader, nor, in some de gree at least. of scientific value.