Histological Studies in the Artemisia Formation

Many investigators have written on the subject of leaf histology and morphology in general, and a few have, in addition, touched upon the physiological significance of structures found during the progress of the study. Among these writers are Haberlandt, Pick, Stahl, Bonnier, Wagner, Hesselmann, and Clements. Most of the work, however, has been purely histological or morphological with little or no reference to environic forces. But in these later days of the development of the new ecology those forces or factors which have been potent in the evolution of plants and which are moulding plants today have come under careful observation and study, not only from the qualitative point of view, but also from the quantitative standpoint. Among the \u27most important of these studies is the one by Dr. E. S. Clements on The Relation of Leaf Structure to Physical Factors, in which the author measured very carefully the physical factors which were operative in the production of the structures which she recorded. However, most of the above studies have been more general than the one here reported. The authors have attempted to cover a greater mass of vegetation rather than to confine themselves to a single unit or a sul?division of vegetation. As indicated in the title, the study given here was made in a definite area or unit of vegetation-the Artemisia formation. This study does not include all of the species of the formation, but twenty-eight of the prominent ones. The original thought was to make a careful study of the leaf histology of some of the more typical plants of this formation in relation to the physical conditions and to determine to what extent the leaf structure of the plants of the formation coincided with the present conception of xerophytic anatomy. An attempt was also made to discover the range of variation in physical factors, especially of water-content, of the formation and the bearing of this variation upon structural phenomena