Schweinfurth landed at Suakin in September, 1867. Before proceeding on his voyage up the White Nile, he resolved to commence with a preliminary exploration of the mountains to the south and west of Suakin between the end of the Nubian Alps and the beginning of the Abyssinian highlands. This elevated district lies for the most part within the watershed of the Atbara’s tributaries, though it also sends down intermittent torrents to the Red Sea. In the mountains to the south of Suakin first appears to any traveller coming from Egypt and the north the characteristic vegetation of tropical Africa, especially such types as the dragon trees (_Dracænæ_) and arborescent euphorbias. These types begin at an altitude of about two thousand feet, as at that height they obtain some moisture, whereas lower down the country is mostly an arid desert. The Nubian _Dracænæ_ and those of the slopes of the Abyssinian tableland are relatively dwarfish (at most some twenty feet high) compared to the giant forms of these tree-lilies which are met with in equatorial Africa. Aloes, of course, grow in the same districts as the euphorbia and the dracæna. “Found in company with them is a wild, unearthly-looking plant called the ‘Karaib’ (_Bucerosia_), of which the branches are like wings, prickly and jagged round the edges like a dragon’s back. They produce clusters of brown flowers as large as one’s fist, which exhale a noxious and revolting smell, the plants themselves being swollen with a white and slimy poisonous juice.” Another item in this harsh vegetation is the _Sanseviera_, a plant belonging to the same group as the aloes, lilies, and dracænas, with isolated, leathery leaves like sword blades, though sometimes with rolled edges like a thick, leathery whip. Higher up, at altitudes of from four thousand to six thousand feet, the trees are covered with clusters of _Usnea_ lichen. On the northern spurs of the Abyssinian highlands is found the wild olive tree, “of low bushy shape, with box-like foliage.” The wild olive is found nowhere else in tropical Africa beyond the Abyssinian region. All watercourses with a supply of moist soil under ground just sufficient for a few months’ vegetation are comprehended within the Arab designation _Wadi_. Cheerless through the dry season, after the first rain their level sand flats are clothed with the most luxuriant flora; fresh-springing grasses put forth their pointed leaves and give the sward the appearance of being dotted with a myriad spikes; then quickly come the sprouting blades, and the river bed is like a waving field of corn. Half-way between Singat and Erkowit Schweinfurth halted at a wady of this character, which bore the name of Sarrowi. He writes:--