264 welwitsch's afkican freshwater alg/e. 



to study Carer, lot him go to Dr. Boott's cabinets ; the specimens 

 are alphabetically arrangecl, and, with Watson's aiid Borrer's 

 her])aria, will answer all general queries. I have to thank the 

 staff of tlie British Museum and Kew Herbaria for ever-ready help 

 in any difficulties. 



WELWITSCH'S AFIIICAN FEESHWATER ALG/E. 



By W. West, F.L.S., and G. S. West, A.R.C.S. 



(Plates 3G5-370.) 



(Continued from p. 2io.) 



3. NosTocHOPSis Wood (18G9). 



1. N. LOBATUS Wood in Proc. Amer. Phil. Soc. Pltlladdphui, 127 

 (1809); in Smithson. Contrib. Knoivl. (1874), iii. 45, t. iii. f. 0; 

 Born. & Flah. I.e. 80 (1887). Crass, fil. 2-0 /x ; diam. heterocyst. 

 5-5-7 /x. 



Golungo Alto. Ad rupes inundatis in rivulo Muria pr. Muria 

 sparsius ; Sept. 1854, No. 201. 



The examples of this are very fine ones, and agree well with the 

 figure given by Wille (in Bihang t. K. Sv. Vct.-Akad. Ilamll. Bd. 8, 

 no. 18, t. i. f. 1-19), with the exception of the cell-walls ; portions 

 only were as moniliform as the previously-found African examples. 

 (Cfr. West & G. S. West in Joxirn. Bot. 1890, 381, t. 301, f. 1-2.) 



The cell- walls are very thin indeed, not any more appreciable 

 than the cell-walls in the ordinary vegetative cells of a Nostoc. 

 The majority of the heterocysts are lateral, globose, and either 

 sessile or stalked (usually supported on one or two cells) ; sometimes 

 they are intercalary, and then they are always elliptic-oblong. 



XVII. ScYTONEMACE^E. 



1. SCYTONEMA Ag. (1824). 



1. S. ciNciNNATUM (Klitz.) Thur. in Ann. Sci. Nat. Ge serie, Bot. 

 i. 380 (1875); Born. & Flah. /. c 89 (1887). Calothrix lanata Kiitz. 

 Alijar. Aq. Bute. Dec. I. no. 5 (1833). 



Var. jETHiopicuM, var. n. Var. pseudo-ramis filo primario dia- 

 metro paullo tenuioribus, cellulis in parte mediana pseudo-ramorum 

 quadratis vel diametro longioribus. Crass, fil. prim. 25-30 jx, trich. 

 17-18 /i ; crass, pseudo-ram. 19-21 jx, trich. 9-5-11-5 fx. 



Paugo Andongo. Alga nigrescens, lubrica, tenax, rhizomata 

 Xyridearum aliarumque plant, palustrium, in spongiosis crescentium, 

 crassis membranis obducens, matricibus tenaciter adha^rens — sicque 

 imprimis loca spongiosa formans. Cum PHchotridte [/i/psopliila et 

 Mowjeotia irref/ularl in pascuis spongiosis breve graminosis juxta 

 rupes gig. prope Catete ; May 1857. No. 111. 



2. S. RivuLARE Borzi in Nuovo Giornale Bot. Ital. xi. 373 (1879) ; 

 Born. &Flah. I.e. 91 (1887). 



Pungo Andongo. Ad muscos rupestres rivulos crescentes per- 



