Th,- Freshwater Algae of Africa. 



:,n 7 



Samples 14, I-"). 



Long, cell., 24-34 // ; lat. cell, 3-4*5 /t. The Alga in question 

 always consisted of four acuminate cells, with hyaline tips, the two 

 middle ones straight, with flat outer and curved inner fares, the two 

 outside ones more or less strongly curved (Fig. 7, a). No other 

 number or arrangement of the cells was observed, excepl for single 

 cells or groups of two or three, no doubt produced by breaking up of 

 the colonies. It should particularly be emphasised that the attenua- 



Fig. 7. — a. Scenedesmus acuminatum (Lagerh.), Chod. h. Front view, 

 ami e, end view of .S'. quadricanda (Turp.), Breb. var. ilis/ior (Breb.), 

 Brunnthaler. c. Ordinary form, and' rf, extreme form of ,S'. obliquus 

 (Turp.), Kuetz. var. dimorphus, Rabenh. All figures x 900. 



tion of the cells extends almost continuously from the middle to the 

 two ends, and that the prolonged apices are always colourless, the 

 chloroplast only occupying the broader part of the cell. In most cases 

 this is due to the fact that the acuminate ends are strongly thickened, 

 the lumina being more or less completely obliterated . In my material 

 the four cells were always placed edge to edge, but Lageidieim {loc. 

 rit.), Chodat (loc. clt.), and Turner (Freshwater Algae of East 

 India. K. Sv. Vet.-Ak. Hand!, xxv, No. 5, 1892, Tab. XX, fig. 30) 

 show T them as partly overlapping. 



It appears from specimens* examined at the British Museum that 

 this species has a tendency to depart from the typical Scenedesmus- 

 grouping and at times to show quite an irregular bunching of the 

 cells. It is probably this feature which has led to its being inter- 



* Viz. Wittrock et Nordstedt, Alg. exsicc, No. 441 ; Wittrock, Nordstedt, et 

 Lagerheim, Alg. exsicc, No. 1242; and Hauck et Richter, Phycol. universalis, 

 No. 692. Some of these show S-eelled biseriate colonies of S. acuminatus. 



