BOTANY OF SOUTHERN RHODESIA. 487 
The Bugenia cordata Formation. 
The extreme edge of the cataract is only aecessible from 
Livingstone Island. As the river goes down, pools of stagnant 
water are left on the rocks of the Island and a bog type of 
vegetation results. The little terrestrial annuals Utrieularia 
Kirkii and U. firmula, and the aquatic U. exoleta, Ericaulon 
subulatum, Canscora Kirkti, Xyris multicaulis, with Denekia 
capensis, Floscopa glomerata, and Hemigraphis prunelloides 
cover the rocks. Overhanging the very edge of the cataract, 
Hygrophila cataracte with Pycreus Mundtii, Scirpus paludicola, 
Cyperus Haspan var. B. americana form dense grass-masses, 
and young Eugenia cordata in every stage of growth seem 
to be gaining ground. ‘These latter show at intervals all 
along the face of the Falls. On the opposite side of the 
cataract-gorge is the so-called Rain Forest, the dominant type 
of which is Eugenia cordata (Pl. 17); but it does not occur on 
the edge of the cliff, as on the cataract side, a fringe of what 
we might eall bog intervening, and this bog-fringe widens con- 
siderably towards Dauger Point, where the spray falls thickest 
when the river is in flood. In this area the soilis very thin, 
and the spray condensing on the surface does not drain off; the 
same plants occur as on Livingstone Island, aud we get also 
Nesea floribunda, Rotala longistyla, Fuirena Œdipus, and a 
dense tangled growth of Pollinia villosa with the sedges given 
above. This bog-area is succeeded by the more or less straight 
line of the Eugenia cordata fringe, which thins out to a single 
tree in the direction of Danger Point. Most of these Eugenias 
are very old, with prostrate trunks, and this is also the case 
with many of the figs. The other Rain Forest trees, lianes, and 
shrubs seem to be more or less the same as those observed on 
the upper banks of river and islands, as far as could be seen at 
this season. In the only two places where the trees of the Rain 
Forest come to the edge of the cliff they follow two little streams, 
but in each case the branches do not overhang, but are clipped 
vertically, absolutely parallel with the face of the cliff. Professor 
Penck, of Berlin, gave me what appears to be the only possible 
explanation of this phenomenon, which is, that the enormous 
mass of water falling over the opposite cliff, 400 feet deep, carri: 
down with it a very large volume of air, which, rushing up the 
opposite face, effectively prevents any vegetative overgrowth. 
LINN. JOURN.—BOTANY, VOL. XXXVII. 2N 
