IHK I'LANT ECOLOGY OF DIIAKENSBERG RAISIGE. 555 



cliffs in the Drakensberg- at points many miles apart, so that 

 it will be seen that the succession indicated is a very extensive 

 one, and probably it extends throughout the whole range. 

 During the dry weather the algal covering dries up and 

 peels from the rock in small flakes, but it does not disappear 

 to any great extent or leave the rock again bare. 



Different types may be recognised, representing various 

 stages in the succession, as follows : 



(1) Cliffs. — Dry, sunny cliffs, or freshly broken rock 

 surfaces, completely devoid of vegetation. 



(2) Cliffs which remain almost but not quite dry. Blue- 

 green algffi and lichens form a hard encrustation which can 

 be scraped off with difiiculty. 



(3) Cliffs which mostly remain dry, but are occasionally 

 completely wet. The Cyanophycefe, which become slimy 

 Avhen wet, and lichens continue here, also bryophyta, both 

 mosses and hepatics, begin to invade. Sub-types may be 

 distino'uished according- to whether the cliffs receive much 

 or little light. The following species were collected by the 

 writer in the Mont aux Sources region and identified by Mr. 

 T. R. Sim: 



Heliophilous species. — Campylopus chlorotrichus 

 (J. M., Grimmia apocarpa Hedic, Tortella casspitosa 

 8cav., Brachymenium pulchrum, Andreaea sp., 

 Campylopus sp. {sji. nov.). 



Ombrophilous species. — Plagiocliila corymbulosa 

 Fears., P. javanica N. S,- M., Thuidiuni tamariscinum 

 Iledw., Macromitrium lycopodioides Burch. (also Epi- 

 phytic on trees), Frullania diptera Nees., Brachy- 

 thecium sp., Orthotrichum sp., Didymodon .sy. 

 710V. ?, Hypnnm cupressif orme L., Bryurn stellipilum 

 C. M., Rhodobryum syntrichioides (C. M.) Par. 



(4) Rock Flushes. — The substratum is here continually, 

 •or almost continually, wet, like it is near minor waterfalls, etc., 

 where the water trickles over the rock face. Blue-green 

 algas are again found in places where there is continual drip, 

 particularly in sunny situations. Collections of these have 



