Page:The Journal of Indian Botany.djvu/362

316 THE JOURNAL OF INDIAN BOTANY. phorbla thymifolia Burm., Boerhaavia repens L., Vernonia cinerea Less., Corchorus antichorus Eoeusch., Launea asplenifolia Hook, and Heliotropium strigosum Willd. Equally persistent and xerophytic are two undershrubs, Calotropis procera Br. and Tephrosia purpurea Pers., and they show a similar reaction to the extreme aridity of the hot season.

It must be emphasized that the entire area is subjected to merciless grazing. Where overgrazing progresses too far, the dry meadow grasses are nearly or quite exterminated (Fig. 14), and a com- paratively worthless grass, Aristida adscenscionis L. becomes domi- nant. It grows up quickly at the beginning of the rainy season, and dies out with the increasing dryness of cold season. It is fairly good for grazing while green, but when mature the awned fruits render it worse than worthless. The appearance of this grass marks the last stage of the exploitation of the plant resources by man. When it dies the ground is left bare except for a few scattering half dead tufts of the typical dry meadow grasses, and some of the more persistent of the rosette weeds.

Thorn scrub stage. Under existing conditions by far the larger part of the uncultivated area about Allahabad is in the dry meadow stage, the modified climatic climax. There are a few scattered areas that give a clue to what the next stage in the vegetation would be if left free to develop naturally (Figs. 12 — 15). This stage is here called provisionally " thorn scrub", for that probably -"is whafc it most closely resembles in its present condition. Nowhere is it to to be found fully developed. To complete the picture we must patch together two quite separate types : (l) areas protected from grazing, such as military and dairy grass farms (Fig. 12), and (2) uncultivated areas that bear a scattering growth of thorny shrub and small trees (Figs. 13-15).

The grass farms owe their more advanced ecological state to protection from grazing. The vegetation is practically limited to grasses and a small number of associated annual and perenrjial herbs. The grass is permitted to grow undisturbed to maturity, when it is cut for hay. All the cutting is done by hand, and not only the grasses but all vegetation impartially is cut off close to the ground. Such a method of harvesting very effectually prevents the develop- ment of shrubs and trees. The characteristic grasses of these pro- tected meadows (Fig. 12j are Apluda varia Hack., Cenchrus biflorus Roxb., Andropogon annulatus Forsk., A. contortus L., Paspalum sanguinale Lamk., Anthistiria imberbis Retz., Iseilema laxum Hack., and I. wightii Anderss. It is difficult to determine which of these grasses is the most important. Apluda varia, a tall coarse grass, ig