WELWITSCH's AFRICAN FRESHWATER ALG^E.' 79 



Berlin (1831), 68 (1832); Ralfs, Brit. Desm. 1G4, t. xxvii. f. 2. 

 Vibrio acerosus Schrank. 



Var. ANGOLENSE, vai". n. Var. major, cellulis lateribus parallelis 

 prope apices rotuudatos atteuuatis ; membrana achroa glabraqiie. 

 Long. 780 // ; lat. 38 /x. 



Golungo Alto. Ad margines stagnorum livi Cuango; Aug. 

 1857. No. 155, 



4. C. TURGiDUM Ehreub. Infus. 95, t. 6, f. 7 (1838) ; Ralfs, /. c. 

 165, t. xxvii. f. 3 (1848). A shorter form than the typical one ; 

 long. 504 /v. ; lat. 61 /x. 



Mossamedes. In stagnis exsiccatis ad ripas flum. Bero ; June 

 1859. No. 171. 



5. C. Leibleinii Kiitz. in Linnaa, viii. 596, t. xviii. f. 79 (1833) ; 

 Ralfs, he. 167-8, t. xxviii. f. 4 (1848). Two forms :— 



Loanda. In stagnis ; Febr. 1858. No. 136. Lat. 38 /x. 

 Pungo Andongo. In stagnis prope Anbilla (Condoj ; March 

 1857. No. 177. Lat. 22 fx. 



6. C. REGULARS Brcb. in Mem. Soc. Imp. Sciences, Clierhoitn/, iv. 

 148-9, 304, t. ii. f. 35 (1856). 



Forma minor. Lat. 18 /x ; apicibus 173 /x inter se distantibus ; 

 striis (ut visis) 15. 



Huilla. Cum Nitella sp. in stagnis pr. Catumba ; April 1860. 

 No. 189. 



Some algologists appear to confuse this plant with C. costatum 

 Corda ; it is, however, very distinct from it. 



5. DociDiuM Breb. (1844). 



1. D. trigeminiferum, sp. n. (tab. 368, figs. 32-34). D. medi- 

 ocre, diametro 16-21 -plo longius ; semicellulte elongat;^, levissime 

 inflatae ad basin, apices subtruncatos versus sensiin attenuatae, 

 lateribus subrectis ; granulis 6 circa inflationem levem ad basin 

 semicellularum in paribus distinctis tribus ordinatis, base semi- 

 cellulae leviter augulari ; membrana dense punctata. Long. 230- 

 322 /x; lat. has. semicell. 16-18 /x, med. semicell. 14-14-5 /x, apic. 

 9-5-10-5 /x. 



Huilla. In paludibus exsiccandis ; April 1860. No. 176. Etiam 

 inter Utricidariam ecalcaratam, Morro de Lopollo ; April 1860. 

 No. 179. 



This species is readily distinguished from D. haculum Breb. by 

 the much slighter basal inflation with no constriction above it, and 

 by the different basal granules. 



6. Pleurot^nium Niig. (1849). 

 1. P. sparsipunctatum, sp. n. (tab. 365, fig. 10). P. raagnUm, 

 diametro circiter 22-plo longius ; seraicellulaB levissime attenuata?, 

 cum inllatione basali permagna, lateribus cum undulis minime 

 profundis circiter 5 supra inflationem basalem, undulis gradatim 

 minoribus apicem versus continuis ; apicibus truucatis, tuberculis 

 magnis rectangularibus 14 (visis 8) insti'uctis; membrana delicate 

 scrobiculata, scrobiculis 5-6-5 /x inter se distantibus. Long. 730 /x ; 

 lat. bas. inflat. semicell. 50 /x ; lat. apic. 28 /x. 



