Chief sudd plants.The most important sudd plants are, without doubt, Papyrus, “Um sûf” (Panicum pyramidale), and “Bus” (Phragmites communis).
“Um sûf” is probably the greatest source of blocks in the river courses, as it seems to thrive in deeper water than either the “Papyrus” or “Bus.” But all these give out long rhizomes. Those of the “Bus,” which is a very tall reed, extend sometimes quite 20 yards from the parent plants. These rhizomes either break away when the new shoots have developed and go to form new colonies elsewhere, or they are driven by the side of the others and gradually encroach on the river.
Among the climbers which bind the new growth (as well as the old) together, the principal are three kinds of Ipomœa, one vine and a leguminous twiner Vigna Nilotica. One of the Ipomœas (I. Reptans) deserves special mention, as it is not only a twiner, but possesses also tubular rhizomes, which enable it to float along the rhizomes of Papyrus, “Bus,” or “Um sûf,” and to knit them together as soon as they give out shoots. Among other plants which have also hollow stems are Jussiæa diffusa, which is also supplied with bunches of spine-shaped floats, and Polygonum tomentosum.
When all these floating masses are being tied together by the twiners the river brings down other plants as a packing to fill the interstices. The most common is Pistia Stratiotes, but there is also a constant supply of Ceratophyllum, Utricularia, Vallisneria and other plants of the same family; also Trapa bispinosa (the water-nut), Potomogetum, Azolla, etc. Little nooks are thus enclosed by runners from the Bus reed, the interior spaces of which are crammed with smaller plants.
It appears wonderful that with all this enormous mass of vegetation growing in these vast swamps in which no traces of human habitations can be seen, the natural decay of the plants does not gradually raise the level of the soil and force the water to keep to well-defined channels which, with the greater volume of water which they would contain would soon force for themselves a less winding course than they now follow.
Action of fires.It appears that one of the chief causes of continuation of the old order of things is fire. Sparsely inhabited as the swamps are, they are swept through from end to end by fierce fires which carry everything before them and kill nearly all the trees which attempt to gain a footing. Here and there a few Kakamut, Dôm, Deleib, Dabka or Talh have managed to spring up, but they are so scattered that they do not count. The papyrus and reeds, instead of dying a natural death and forming soil by decay, are burnt down, and what of the ashes is not blown away by the wind is carried away by the next flood. Were it not for these fires it is probable that trees of the species mentioned above would spring out more abundantly, and it would not be a difficult matter to define the banks of the channel by plantations of these or other river-side trees, such as are to be found in Ceylon, for example, lining the river, e.g., Terminalis glabra, Vitex Leucoxylon, Vateria acuminata.
Recent history of blocks and sudd-cutting. (Various.)In 1863, 1864, and 1868, heavy sudds blocked the Bahr El Jebel, and in the first mentioned year they extend to the north of Lake No.
In 1870, Sir Samuel Baker found the Bahr El Jebel closed with sudd at its mouth in Lake No. He attempted to ascend the Bahr El Zeraf but failed to reach the Upper Nile, and was obliged to return.
In 1871 he ascended the Bahr El Zeraf, and eventually forced his way into the main river near Shambe, literally lifting his boats and steamer over the intervening swamps and shallows.
In 1872 both the Bahr El Jebel and Bahr El Zeraf were closed, and in 1874 Ismail Pasha Ayub cleared away the sudd in the former river.