242 welwitsch's African freshwater alg^e. 



singulis vel gemiuatis, longis et flexuosis, filo primario diametro 

 tenuioribus, interdum ramosis, vaginis crassis et plerumque achrois, 

 cellulis variabilibus, lis filorum primariorum similibus, ssepe in- 

 distinctis ; protoplasmate pallide aerugiuoso et minute granulate ; 

 heterocystis intercalaribus, rectangulari-oblongis (diametro lJ-3^- 

 plo longioribus) ; sporisnonvisis. Crass, fil. prim. 11'5-12-5/x; diam. 

 cell. 7'5-8/a; crass, ram. 6'5-9'5 /m, diam. cell. 4-6-5 fi; diam. 

 heterocyst. 6 )U. 



Huilla. Inter Schizotrichem fuscescentem, in paludibus exsic- 

 candis ; April 1860. No. 176. Etiam inter Utricnlanam, Morro 

 de Lopollo ; April 1860. No. 179. 



This has a very distinct facies from H. luteolus, being of a bright 

 golden brown colour, with more tortuose filaments, the sheaths of 

 which have a very different appearance ; the cells also are much 

 more variable (and usually longer), the branches are more numerous 

 and of a different thickness to the primary filaments, and often 

 arise in pairs. 



3. H. intricatus West in Journ. Linn. Soc. xxx. 271-2, pi. xv. 

 f. 16-28 (1894). An aquatic form ; spores rectangular oblong, 

 1^-3 times longer than broad. Crass, fil. 5-5-7 /x. 



Huilla. In caespitibus parvis intricatis inter H. hiteoluin, in 

 uliginosis editioribus, prope Humpata, Empalanca et Lopollo ; 

 May 1860. No. 15. 



4. H. Welwitschii, sp. n. H. inter alias algas aquaticas 

 sparsus, flavo-feruginosus ; fills primariis subflexuosis, vaginis 

 arctissimis, indistinctis et hyalinis, e serie singula cellularum 

 formatis, cellulis iurequalibus, diametro aaqualibus vel paullo 

 longioribus (raro duplo longioribus), subglobosis, subquadratis vel 

 oblongis ; ramis frequentibus plerumque uuilateralibns, brevibus, 

 patentibus, filo primario diametro requalibus vel paullo tenuioribus, 

 subatteuuatis, vaginis achrois, arctis sed distinctis, cellulis varia- 

 bilibus, diametro ^-3-plo longioribus ; heterocystis rarissimis, 

 intercalaribus, rotundo-quadratis vel rectangulari-oblongis ; sporis 

 subglobosis vel oblongis, polls rotuudatis (diametro 1-2-plo longi- 

 oribus). Crass, fil. prim. 5-5-7'5 /* ; crass, ram. 3"5-5'5 /x; hetero- 

 cyst. 6-8 /x X 6 /a; spores 5-8-5 n x o jj.. 



Pungo Andongo. Inter Batrachospenno (/racUlinio in rivulo de 

 Tangue ; May 1857. No. 3. 



This species may be compared with H. hibeniicus West & G. S. 

 West (m Jonrn. It M. S. 1896, 163), from which it differs in the 

 longer cells of the primary filaments ; in having much fewer 

 branches, whicli are also shorter and not flexuose ; moreover, the 

 cells of the branches, as well as the heterocysts, never attain the 

 length of those of H. Iiibeniicus. Compare also with H. intricatus 

 West. 



2. Stigonema Ag. (1824). 



The cells of this genus are protoplasmically continuous through- 

 out the whole plant, a fine strand of protoplasm, passing from cell 

 to cell along the middle of the filament, effecting this continuity. 

 This is best seen in plants that have been dried and soaked out, the 



