TRANSACTIONS OF SECTION K. 587 
the hydrophilous and hygrophilous formations, which we find especially in equa 
torial Western Africa and eastwards to the Bahr-el-Ghasal. 
After the hydrophilous formations we come to the hygrophilous, those whose 
vegetation is directly influenced by the atmospheric water. These formations are 
also very varied; thus we have those of the lower regions, which are megatherm, 
others of the middle regions, which are mesotherm, and others of the higher, cloudy 
regions, which are microtherm. 
There are also many formations which one can name subxerophilous, and which 
belong to regions with a short rainy season, or limited deposit of mist; they are 
very numerous in the plains as well as in the mountains. 
Finally we come to the true verophilous formations, which receive very little 
rain, and that during only a short period of the year, or only dew at night-time. 
These formations are botanically of the greatest interest, because they show the 
most singular adaptations to the dry climate, which are well known to all botanists, 
who know some of the plants of the Karroo, of Namaqua- and Damaraland, of the 
dry East African steppes at the northern foot of the Usambara mountains, in 
Somaliland, and in the Sahara. 
List of the principal Formations. 
A, Hatopuitous Lirroran Formarions.—Mangrove—Littoral serub—Her- 
baceous vegetation of sandy beech—Littoral rocks—Creeks, 
B. Hyprornitous Formarions.—Forest on alluvial soil or gallery-forest. 
a and b, hydrophilous and hygrophilous. (a) In very warm districts with abun- 
dant rainfall—(a) in West Africa; (8) in East Africa (6) In districts of medium 
warmth with abundant rainfall. (c) In districts very warm with a scarce rainfall. 
(d) In districts moderately warm with scarce rainfall. 
Alluvial country without trees (a, }, c, d, as before).—Tormation of the Podoste- 
monaceve in fast-running mountain streams and torrents—Formation of the lakes— 
Shallow pools—Pools with mixed plants—Marantacez (Clinogyne)-pools—Vossia- 
pools—Phragmites-pools—Papyrus-pools—Typhonodorum-pool (on the Isle of 
Zanzibar). 
C. Hyeropxitous Formarions.—(a) Megatherm : Formation of the lowest ever- 
green rain-forest [(a) in West Africa; (8) in East Africa]. Middle evergreen 
rain-forest (varying in altitude from 400—1,300 m. above the sea, corresponding to the 
various altitudes of the mountains and ridges, [a, slopes; 8, glades, clearings; 
y, gullies.|—Upper evergreen rain-forest [a, slopes; 8, glades; y, gullies]. Less 
moist rain-forest on slopes exposed to dry winds. (6) Mesotherm: Moist pasture 
ground—Bamboo-forest of the mountains—Forest in the cloud region of the higher 
mountains. 
D. SusxerorHitous Formations.—Formation of the park-like woods in the 
coastal regions—Borassus groves—Hyphwne groves—Formation of the fertile 
submountainous region with red soil—Formation of the upper fertile submoun~ 
tainous region with black soil—Formation of the mixed mountainous forest on 
drier slopes—Formation of the mountain scruab—Mountain scrub with Pteridium— 
Mountain heath—Formation of Pteridiwm [(a) primary ; (6) secondary }—Moun- 
tain scrub-steppe (steppe grass with shrubs)—Mountain tree-steppe—Rocky 
summits and slopes of the mountains—Stony slopes with humus—Formation of 
the shingle slips—Sunny flat rocks—Sununy rocky declivities—Dry mountain pasture- 
apenas Uppae dry mountain meadows—Upper dense scrub—Subalpine dwarf 
shrubs. 
E, Xeropuitous Formations —Saline ‘steppe’—Steppe with various succu- 
lent plants—Steppe formation of the evergreen thorn shrubs and trees (Euphor- 
bia)—Aloe-steppe (with numerous high Aloes)—Steppe of the deciduous-leaved 
spiny shrubs—Grassy ‘ orchard-steppe’ (Obstgartensteppe, with scattered small 
spiny trees)—Mixed thorn- and shrub-steppe—Open grass-steppe—Grass-steppe 
with scattered trees, 
While the vegetation is characterised by physiological types, the flora is 
characterised by the systematic position of the plants. There is no doubt that in 
