514 Bulletin American Museum of Natural History [Vol. LIII 
Lake Edward sometimes exceed 2,500 m. and even very rarely reach 
3,000 m. There is then a beginning of subalpine zone of Ericacez, but, 
as such areas are always of small extent, they never form a formal life 
Zone. 
- Conditions are, however, quite different on the Mfumbiro Volcanoes, 
which rise considerably higher. They form a chain of eight isolated peaks 
north of Lake Kivu: Mt. Ninagongo and Mt. Namlagira in the west; 
Mt. Mikeno, Mt. Karisimbi, and Mt. Vissoke in the center; Mt. 
Sabinyo, Mt. Mgahinga, and Mt. Muhavurain the east. The two highest 
of these are Mikeno (4,434 m.) and Karisimbi (4,500 m.) and, though 
they are not covered with permanent ice, they nevertheless offer a 
succession of life zones somewhat similar to that of Mt. Ruwenzori.! 
The two western volcanoes are still active and their slopes are covered 
with recent ashes and lavas. The various plant formations are, therefore, 
still in an incipient stage and, as even now they are occasionally disturbed 
by fresh eruptions, they cannot be expected to show a well-defined 
altitudinal succession. On Mt. Ninagongo, for instance, the lowest 
zone, between 2,300 m. and 2,800 m., is covered with peculiar thickets 
of low trees and bushes, occasionally mixed with bamboos (Arundinaria 
alpina K. Schumann), and evidently the first stage of a mountain or 
cloud forest. Above 2,800 m. begins a formation of subalpine bushes, 
with Hrica arborea Linnzeus and Myrica salicifolia Hochstetter as main 
elements, in which are scattered numerous high and low herbaceous 
plants, while mosses and lichens are very abundant. The highest 
points, around the rim of the crater, form an alpine or Paramos region 
with tree groundsels (Senecio Erici-Rosenit Fries) and Helichrysum. The 
torch lobelias, however, have apparently not yet taken a foothold on the 
summit of Ninagongo. The malacological fauna of this volcano is still 
very little known, only four species having been recorded thus far, all 
obtained by Schubotz, between 2,500 m. and 3,000 m.: Limicolaria 
saturata, Marconia latula, Gonaxis vulcani, and Cerastus vexillum. 
The other volcanoes have become extinct centuries ago, so that the 
various plant formations which cover their slopes have had time to 
mature and to reach their climax, and now form regular altitudinal zones. 
Their alpine zone contains, in addition to Senecio Erict-Rosenii Fries, also 
giant torch lobelias (L. karissimbensis R. E. and Th. Fries and L. Wol- 
lastonit Sp. Moore). Moreover, the similarity of the plant growth of the 
Mfumbiro group as a whole with that of the Ruwenzori Range is ex- 
1The vegetation of the Mfumbiro vole is di by A. ‘Di - 
walt ee ae anoes is discussed by Engler, 1925, ‘Die Pflanzen 
