Page:The Journal of Indian Botany.djvu/462

 46. Flaveria contrayerba Pers — Not common ; not in a good condition.

47. Evolvulus alsinoides L— Rather common in poor soils.

48. Lippia nodiflora Michx.— Not very common.

49. Achyranthes aspera L.— Not very common. A very hairy plant.

50. ABrua javanica Juss. — Not very common. A very hairy plant.

51. Aristolochia bracteata Betz. — Occasional.

GRASSES.

52. Pennisetum Alopecuros Ness.

53. Ischaemum pilosum Hack. — Very common in black soil fields where it shows large dry patches which were dug up and fed to cattle.

54. Andropogon pertusus Willd.

55. Andropogon annulatus Forsk.

56. Cynodon dactylon Pers.— Found green only near moist places from where they were dug up and fed to cattle.

All these grasses dry up in the absence of water but sprout again when it is available.

When we try to consider the points brought out by the above observations the first thing noticed is that according to the nature of the soil the amount of available moisture varies roughly from 1-4 per cent, during the hottest and driest part of the year. In the sands the available moisture was under 1 per cent. In the course 'murum' soils it was between 1 and 2 per cent. In the black soils with their very large amount of clay the available water even at this time rose to between 3 and 4 per eent. This seems to be the limit of growth of any phanerogamic vegetation whatever on these various classes of land.

A general reduction in the size of the plant and of its aerial parts such as branches, leaves, &c. and the development of a tap root (diagrams of some of the typical roots are attached) were characteristic, though the latter was not quite universal. There are two dicotyledons in the list which even under the very highly xerophytic conditions did not show an appreciable tap root. The first of these is Tragia cannabina L. and the second Garalluma fimbriata Wall. The primary root of the former of these seems to have been soon divided into several secondary branches. These branches are long and rather stout how- ever, and descend obliquely into the soil so that they can perform the same function as a tap root. This plant is moreover well supplied with other means of decreasing transpiration andhence economising