REPORTS UPON TWO COLLECTIONS OF MOSSES FROM 

 BRITISH EAST AFRICA 



By H. N. DIXON, M. A., F. L. S. 



(With Two Plates) 



I. THE .AIOSSES OF THE DUMMER-MACLENNAN EXPEDITION 

 TO MOUNT ELGON, 1918 



Several sets of the mosses collected on this recent expedition to 

 Mount Elgon have been issued. I have received part of one through 

 Mr. T. R. Sim, of ]Maritzburg ; and I have also had through my hands 

 the sets belonging to the U. S. National Museum and to the Kew 

 Herbarium. The material in many cases is poor, but in others it is 

 good ; and though the v^'hole collection is not large, consisting of 

 about 50 numbers (many of which, however, contained several 

 species), it contains some interesting novelties, notably a species 

 of Holoimtriuni quite distinct from any of the African species, a 

 fine hew Bryum of the Rosulata group, and an interesting new 

 Braiinia. The types of these and of the other novelties are in the 

 L'. S. National Museum ; duplicate types are in my own herbarium. 



An unusual feature of this collection is the number of species 

 generally rupestral, which were here epiphytic. This is notably the 

 case with Grimmia ovata Web. & Mohr, Amphidhmi cyathicarpum 

 (Mont.), Anomohryum robiistum (the species of this genus are 

 normally rupestral or terrestrial), Bryum alpinum Huds., Hedivigia 

 albicans (Web.), and Ectropothecium latcriticolum Broth. The 

 suggestion may be hazarded that these mosses formed the ancient 

 flora of the crater, at the time when it was mostly unclothed with 

 vegetation, and that as the phanerogamic vegetation increased and 

 covered the rock surface the mosses were driven to the only sub- 

 stratum left for them, viz, the stems of the tree heaths, and other 

 wood, Hving or dead. 



In the following list the abbreviation c. fr. = fruiting, and st.= 

 sterile. 



Smithsonian Miscellaneous Collections, Vol. 72, No. 3. 



