176 FROM NORTH POLE TO EQUATOR. 



which enclose deep-sunk basins, where pools, ponds, and lakes are 

 formed during the rainy season, while during winter the clayey soil 

 is rent with thousands of fissures. In the deepest and longest 

 depressions there is, instead of standing water, a " Chor " or rain- 

 torrent, that is to say, a water-course which even in the spring is 

 only occasionally in flow, but which, under specially favourable 

 circumstances, may be flooded to the brim in a few hours, and does 

 not merely flow, but rushes a moving wall of water hissing and 

 thundering down the valley, often, however, disappearing before it 

 reaches a true river. Except where there are these water-basins 

 and water-courses, a relatively rich vegetation covers the whole 

 surface of the steppe. Grasses of various kinds, from lowly plants 

 which creep along the ground to great cereal-like stems as tall as a 

 man, form the basis of the vegetation. Trees and shrubs, espe- 

 cially mimosas, baobabs, doum-palms, and christ-thorns, combine 

 here and there, especially near the water, to form thickets or groves, 

 but elsewhere they are but sparsely scattered amid the grasses 

 which so uniformly cover the flats, and it is only at a few spots 

 that they form even a thin wood. Never do the trees show vigour 

 of growth like that seen in the valleys with true river courses, 

 where the blessings of spring are always retained; on the contrary, 

 they are often stunted, usually low and with scraggy crowns with 

 rarely even a twiner struggling upwards. They all suffer from the 

 severity of the long torrid winter, which hardly allows them to 

 gain subsistence, and keeps off almost all parasitic plants. It is 

 different with the grasses which, in the short but abundantly moist 

 spring, shoot up luxuriantly, bloom, and ripen their seeds, and in 

 fact attain to a thoroughly vigorous life. To them the monotonous 

 aspect of the steppe is in great part due, for, humble as they are, 

 they obliterate many of the contrasts which would otherwise be 

 apparent, and the uniformity of their colouring becomes oppres- 

 sively wearisome. Not even man succeeds in introducing variety 

 into this eternal sameness, for the fields which he tills in the midst 

 of the grass-land seem from a distance so like their surroundings 

 that one can scarce distinguish grain from grass. Even the round 

 huts made of slender stakes, with conical roofs thatched with 



