FEESHWATER ALG-^. 



Dbtbeminbd by 

 W. WEST, F.L.S., AND G. S. WEST, B.A., A.E.C.S. 



The algse which form the subject of this paper were collected 

 some forty years ago by Dr. Welwitsch during his eight years' 

 residence in Angola. They are chiefly from the latter region, but 

 a few are from B?nguella and Sierra Leone. The specimens are 

 all dried ones, and for the most part are mounted on paper. Por- 

 tions of all had to be soaked out for investigation, the results of 

 which have been very gratifying, as by this means, after a detailed 

 examination, many of the smaller species have been observed. 

 These latter, however, had not been collected as such, but, inde- 

 pendently entangled among other conspicuous species, had been 

 collected with them. The Desmids had practically all been 

 unconsciously obtained in this way, few, if any, collections having 

 been made from places in which one would expect to find Desmids 

 in abundance ; and yet about 130 fine species (including fifty 

 undescribed ones) have been found as intruders amongst other 

 algse. From these mere samples one is led to wonder as to the 

 richness of the Desmid-flora of Tropical Africa. 



Very little is known concerning the Freshwater Algse of Africa, 

 only a few small scattered papers having as yet been published ; 

 and this extensive collection — one in which almost all the groups 

 are represented — very considerably enlarges our knowledge of the 

 geographical distribution of these plants. 



At the time these algK were collected the great majority of 

 the species were as yet undescribed. They form part of the 

 Welwitsch collection deposited in the British Museum, and the 

 numbers after the species refer to the numbers on the sheets of 

 this collection. A few of the species can hardly be considered as 

 freshwater ones, bvxt as they were in the collection we have 

 included them. 



It is interesting to note that the earliest collection of algse made 

 in Africa has been found to be more extensive and representative 

 than any hitherto described. The species are localised under the 

 various districts of the region, exactly as indicated by Welwitsch 

 on his herbarium labels. (Ex Journ. Bot. 1897, pp. 1, 2.) 



