The relation of certain ecological factors to the inhibition of forest floor herbs under hemlock

In the region of Turkey Run State Park, Parke county, Indiana, there occurs an abundance of Hemlock, Tsuga canadensis. In this locality the tree is to be found typically along the upper limits of precipitous creek bluffs and along the rims of the sandstone canyons,-- here it is the dominant plant in an edaphic climax. The Hemlock association is a codominant climax with the typical Beech-Maple climax of the region

Factors Favoring the Persistence of a Relic Association of Eastern Hemlock in Indiana

Scattered through the deciduous forests of Indiana there are relic colonies of eastern hemlock, Tsuga canadensis. These colonies, with quite an appreciable group of other species, including herbs and shrubs (1), are generally considered as remnants of a previous southern extension of their natural species ranges. After these species had been forced southward by the conditions accompanying the advancing ice caps, their post glacial movements, in keeping pace with the retreating ice masses back to their original climax ranges, were very irregular. Thus, in the course of post glacial reorganization of the vegetation, hemlock as a species resumed its more northerly range found in the Lake Forest which covers the area immediately north of the Great Lakes

The Acid Ranges of Some Spring Flowering Herbs with Reference to Variations in Floral Color

It is of common knowledge, derived from even limited field observation, that color in the petals of many of our native flowers is quite variable. Where these variations seem constant, and are accompanied by other characters, taxonomists use color as one of the bases of species differentiation. On the other hand, some species, such as Phlox divaricata, treated in this paper, show gradations in floral color from pure white through blue and lavender to pink; these variations are evidently unaccompanied by other constant characters which might indicate racial differences