BRYOPHYTA OF S. RHODESIA. 295 



eastwards as at Mazoe, Umtali, Melsetter, Zimbabwe, etc., 

 conditions approach much more nearly to those of the Drakens- 

 berg further south, and in a few localities regular forest conditions 

 occur, bringing with them mosses in abundance. 



Even at Zimbabwe, which is quite in the mist-belt and bush- 

 veld, though not in the forest range, mosses are in great abun- 

 dance, though belonging to few species. One naturally enquires 

 why few species, and it would appear that the dry winter, the 

 granite formation and the strong sunshine, combine to make the 

 conditions sufficiently arid during the winter to kill out such 

 species as are not extremely tenacious of life. 



The Zimbabwe rocks and ruins are wonderfully moss-clad, 

 as also are the rocky kopjes in that region, but it is noticed there 

 that such species that can endure on bare rock, or on soil in rocky 

 crevices, are those which flourish, and that these exhibit very 

 marked pioneer qualities, particularly notable in Ao?igstroemia 

 gymnomitrioid.es Dixon, and in Campylopus. 



In regard to the Zambesi Falls, where the rain forest and the 

 spray-steeped cliffs would lead one to expect mosses in abundance, 

 it is the case that a few species are there in profusion in certain 

 places; a hundred yards away from the gorge in any direction one 

 is again in the arid plateau, mostly sandy, and devoid of all moss 

 vegetation. 



Trees are frequent, mostly of a xerophyllous nature, but no 

 epiphytic mosses occur on them outside the rain forest. The 

 Zambesi has travelled through hundreds of miles of arid country 

 since it left its mid-African forest sources, and the same aridity 

 exists in all directions. Consequently what species occur at the 

 falls are rather a survival of the most enduring, than a full 

 representation of tropical forest moss-flora. The perpendicular 

 and inaccessible cliffs overlooking the falls just beyond the spray 

 limit are thinly clad with succulents but not with mosses, while 

 away from the falls, down the river and where spray is absent, 

 the Zambesi gorge is a deep chasm, where succulents and 

 xerophytes exist and flourish rather than a suitable locality for 

 any other than the most hardy mosses. Up the river, above the 

 falls, the variations of water level render rocks and banks sub- 

 merged for months and then dried out for other months, and so 

 are almost without mosses. 



One hundred and twenty-nine species of mosses, and twenty- 

 four of Hepaticae are now recorded from Southern Rhodesia, of 

 which over eighty mosses and all the Hepaticae were collected 

 during fhe visit of the South African Association for the Advance- 

 ment of Science last year — mostly at the Victoria Falls or at 

 Zimbabwe. 



Twenty-three of these mosses are new to science and are 

 described hereunder by Mr. Dixon, seven others were previously 

 described by Mr. Dixon from Rhodesia as new to science, so 

 altogether Rhodesia has provided recently thirty new species of 

 Musci out of its small total. 



The Hepaticae are all previously known from elsewhere. 



