The road follows throughout the course of the river, rising sometimes 200-300 feet, to pass over rocky spurs; at other times it lies on the surface of the boulder conglomerate, and more rarely close to the river. Here and there is a small village, with a few rice-fields, but the greater part of the valley is utterly sterile. Like the valleys of the outer Himalaya, that of the Sutlej here exhibits a curious mixture of the ordinary vegetation of the plains, with forms which point out the mountainous nature of the country. The whole flora is strongly characteristic of a dry soil and an arid climate. The mountain ranges to the west and south, no doubt, intercept a good deal of rain; and the lofty mountains, 10-12,000 feet in height, which, on the right and left, rise rapidly from the river, appropriate to themselves a great part of the moisture which reaches the valley. We may, therefore, in the absence of direct meteorological observations, infer, from the physical structure of the valley, and from the nature of its vegetation, that its climate is drier than that of the valleys at the base of the Himalaya.
The Sutlej valley cannot, of course, be properly compared with the base of the mountains farther east, where luxuriant forest covers all the slopes; but when contrasted with the Pinjor valley, or the low hills above Kalka, it is only on a careful comparison that a difference is to be observed, and then, perhaps, more by the absence of forms abundant in them than by any marked addition of new ones. The ordinary shrubs of the Sutlej, at 3000 feet, are _Adhatoda Vasica_, _Carissa edulis_, _Colebrookea_, _Rottlera tinctoria_, and some species of _Boehmeria_, all characteristic of the outer hills, and the two first common plains plants. The remarkable _Euphorbia pentagona_ is also common. _Butea_, _Ægle_, and _Moringa_ do not occur, nor are there any bamboos. _Flacourtia sepiaria_, _Capparis sepiaria_, and _Calotropis_, which are three of the commonest plants of the plains, were also not observed. A large white-flowered caper (_Capparis obovata_, Royle) and a glabrous _Zizyphus_ were the most remarkable new forms. The herbaceous vegetation differed scarcely at all from that of the plains, consisting chiefly of species which, during the rainy season, spring up in the lightest and driest soils.