382 Transactions of the Boyal Society of South Africa. 
(hippo rivulet), and lower still, as the Mokolane (palm-tree) river, where 
this small branch ends to-day ingloriously in a small swamp some 13 miles 
short of the north-western margin of the Lake basin. Its failm^e to reach 
the western end of the Lake to-day is no doubt partly attributable to 
diversion of the channels to the north through silting up, but chiefly, I think, 
to the fact of the generally greatly decreased volume of water discharged 
by the Okovango during recent decades. When Livingstone discovered 
the Lake in 1849, this Taoge, or westernmost river, was — according to old 
natives who were young men when the " Doctor " came to the Lake—" a 
large river," and from what the old Makuba state that their fathers told 
them, the Okovango brought down annually a much larger volume of water 
both by the western and by the eastern rivers during the period (about) 
1800-1850 than it has done since, and that even when Livingstone came 
the flow had markedly decreased. 
It appears that the westernmost river, the Taoge, ceased running into 
the Lake at the end of the reign of the Batawana Chief Letsholathebe 
(about the end of the seventies) and that when his son Moremi succeeded 
him, about 1880, it had completely dried up south of the " Mokolane." 
The only water that reaches the Lake to-day flows into it at its eastern 
end, and then only when the Kunyere and Thamalakane Elvers are in high 
flood. When the Kunyere and Thamalakane Elvers are both very full, the 
whole of the Kunyere water and a portion of the Thamalakane water run 
into the Lake. The Thamalakane, which is the largest of all the branch 
rivers, when very full, divides its water at its junction with the Botletli and 
Lake Elver, the larger portion thereof flowing eastwards down the Botletli 
and the smaller portion along the Lake Eiver to the Kunyere confluence at 
Toten, thence into the Lake together with the Kunyere water. On the 
other hand, when the Thamalakane and Kunyere Elvers are low, all 
the water of the former flows down the Botletli, and the water of the 
latter, being dammed by the sand-bar in the bed of the arm of the Lake 
(also called the Lake Eiver) between Totefi and the Lake mouth, makes 
its way eastwards to the Thamalakane-Botletli junction, there joining the 
Thamalakane water down the Botletli. 
N'gamiland, generally speaking, is divided into two zones : the Elver- 
system zone and the Sandbelt zone. In the former zone tropical 
vegetation predominates, and in the latter the sub-tropical vegetation of 
the Kalahari. 
As to the tropical vegetation, two species of palm are plentiful on the 
countless islands in the swamps — especially in those areas north of 
the 20th parallel where there is always water — namely, the tall fan-leaved 
'* Mokolane " or Borassus palm, and the short " Tsaro " palm, with its 
feather-shaped leaves ; and generally, in the river-system zone, the Kigelia 
;pinnata (locally named the " Moporota ") with its huge, pendant sausage- 
