Page:The Journal of Indian Botany.djvu/361

THE ECOLOGY OF THE UPPER GANGETIC PLAIN. 315 Dry meadow stage. The wet meadow merges gradually into what may be called dry meadow (Fig. 11), a very extensive and uniform association dominated by perennial grasses. Under natural conditions it probably would be but an inconspicuous incident in the topographic succession, but due to the retrogressive influence of the very intense human factors, it has become for the time being the climatic climax over most of the area, This stage is connected with the wet meadow by Cynodon dactylon and Eragrostis tenella. The latter is a short-lived annual that flourishes everywhere during the rainy season, and almost completely disappears by the middle of winter.

The typical dry meadow (Fig. 11) is dominated by two perennial grasses, Andropogon intermedins Br., and Elusine aegyptica: Desf. Both are able to produce a luxurient grass cover, but under severe grazing they assume a dense compact tufted habit; both propagate freely by runners. Under excessive grazing the Andropogon is the more persistent. In slight depressions and in the shade of trees, where growth conditions are a little less severe, three perennial Leguminosae, Desmodium triflorum DC, Indigo/era enneaphylla L., and Alysicarpus monilifer DC. are very charateristic components of the dry meadow. They too have the tufted prostrate habit of growth. All are excellent pasture plants, and owe much of their value to their persistence under grazing and drought.

During the rainy season there is a conspicuous development of Eragrostis tenella, and of two annual Leguminosae, Cassia obtiisifolia L. and Grotalaria medicagitiea Lamk. The last two are often so abundant as to give character to the dry meadow vegetation, but they die at the beginning of the cold season, and little trace of them remains in the hot season.

Overgrazing and the intense aridity of the hot season greatly reduce the Iuxurience of the grasses of the dry meadow (Fig. 11), and another important constituent then becomes prominent. This is a series of small xerophytic and very persistent perennials that are able to survive both the grazing and aridity because of the development of effective perennating organs. All have deep tap roots with a perennial crown of stem, and most of them have a well developed rosette habit of growth. As the cold season advances and gradually merges into the hot season, the older and larger leaves fall, the more delicate stems are grazed off or die, and the aerial parts become reduced to a small compact crown of very resistent vegetation. In this condition they are able to bloom and produce seed abundantly. Some of the more common of these plants are:—Convolvulus pluricaulis Chois., LepidagatJiis trinervis'.Nees, Justicia simplex D. Don, Eu-