Hope. — - The ‘ Sadd 9 of the Upper Nile. 501 
£ Um-soof.’ 
The other main factor in the composition of * Sadd ’ is, 
according to Sir William Garstin, the 4 ‘ um-soof* reed. That 
is the Arab name of the plant : the botanical name is, ac- 
cording to Dr. Georg Schweinfurth (the author of ‘ Beitrag 
zur Flora Aethiopiens,’ Berlin 1867, and other works on the 
botany of the Nile Region), Vossia procera , a grass belonging 
to the tribe Rottboellieae. But, says Sir William Garstin, 
‘ the sample of this grass sent to the British Museum was 
identified as Phragmitis communist The specimens of Vossia 
procera in the Kew Herbarium show a thick stem, with long 
and broad sheaths from the nodes which at first envelop the 
stem and make it appear thicker than it really is. It throws 
out roots from each node (or joint), which draw nourishment 
from the water in which it grows, and also from the mud 
should the stems lie prostrate, as probably they at first do. 
Schweinfurth, in the book presently to be quoted from as to 
6 Ambatch,’ mentions Vossia procera as one of the plants which 
have a share in the formation of the floating ‘ Sadd’ islands. 
This must be a comparatively new identification, for in the 
‘ Treasury of Botany,* 1870, it is stated that Vossia cuspidata y 
a native of the West Indies, is the only species of the genus. 
‘ Ambatch.’ 
This plant, Herminiera elaphroxilon, Adanson, the only 
species of the genus, belongs to the order Leguminosae, and 
has ‘ thorny branches, abruptly pinnate leaves, and large 
orange-coloured flowers, succeeded by linear oblong com- 
pressed legumes, which become at length spirally twisted.’ 
Sir William Garstin, as has already been mentioned, says 
that this plant has been unjustly accused of assisting to form 
the ‘ Sadd * in the Bahr-al-Jebel ; that it does not grow in any 
great quantity near that river ; and that its stem is so light 
and brittle that it would break when subjected to pressure. 
But this is not the view Dr. Schweinfurth takes of it. In his 
Mm2 
