224 Chlorophycece 



Var. tumidus . [Rh. polymorphism var. tumidum W. & G. S. West 

 1897.] Cells solitary or in small aggregates, curved, in the middle inflated; 

 apices most acute; length 61 73 p ; breadth 4'5 6'5 p. Chloroplast with 

 one or two pyrenoids, or destitute of them. Fig. 94 D. 



Var. mirabilis . [Rh. polymorphum var. mirabile W. & G. S. West 

 1897.] Cells solitary and considerably longer than in typical A. falcatus, 

 variously curved, often sigmoid ; apices very acute. Chloroplast completely 

 interrupted in the middle of the cell and often fragmented ; vacuoles in the 

 cell- protoplasm often containing a single moving corpuscle. Length up to 

 117 fj. ; breadth 2 3'5 M . Fig. 94 E. 



Var. spiralis . \_Rh. spirale Turn. 1893; Rh. fasciculatum var. spirale 

 Chod. 1902.] Cells grouped in bundles of 4 or 8, twisted round each other in 

 the central region of the cells, but free at their extremities. 



Var. spirilliformis . [Rh. polymorphum var. spirale W. & G. S. West 

 1898.] Cells always solitary, spirally twisted, making 1 1-J- turns; apices 

 very acute. Often occurs in prodigious quantity in stagnant water. 



The above varieties of A. falcatus are widely distributed and some of them 

 are abundant. They occur most abundantly in small ponds, but are also 

 frequent in the freshwater plankton. 



A. convolutus - . \_Rliaphidium convolution Rabenh. 1868.] Cells 

 .solitary, short, only 3 6 times longer than the diameter, lunate or arcuate ; 

 apices very acute ; diam. 3 6 p. 



A. Pfitzeri . [Rhaphidium Pfitzeri Schroder.] Cells straight, some- 

 what asymmetrical, 5^ 6 times longer than the diameter, much attenuated 

 with rounded apices ; forming small colonies embedded in mucilage. Length 

 38 49 /z ; breadth 7 8 p.. In the Scottish plankton ; not uncommon. Fig. 

 94 G and H. Perhaps this species would be better placed as a form of A. biplex 

 (Reinsch) nob. [ = Rh. bipkx Reinsch 1867.] 



A. setigerus - . [Reinschiella ? setigera Schroder 1897; Schroderia 

 setigera Lemm. 1898 ; Rhaphidium sctigerum W. & G. S. West 1901.] Cells 

 fusiform, with the apices much attenuated into tine hair-like prolongations. 

 Chloroplast with one pyrenoid. Diam. 5 - 7 6'5 p; length 75 88 p.. Mostly 

 found in the plankton. Fig. 94 F. 



Genus Closteriopsis Lemm., 1898 1 . This genus only differs 

 from Ankistrodesmus in the great length of the cells and in the 

 consequent increase in the number of pyrenoids. The cells are 

 narrow, greatly elongated, and the extremities are much attenuated 

 into bristle-like points. The Chloroplast contains a dozen or more 

 pyrenoids in an axial series. 



Cl. longissima Lemm. is only known from the plankton. In the British 

 Islands it has been found in Lough Neagh, Ireland, from Finstown, Orkneys, 

 and in Loch Asta, Shetlands. Length 330 p. ; breadth 3'8 4-2 p. 



Genus Actinastrum Lagerh., 1882. The cells are ovoid, 

 oblong or club-shaped, from three to six times longer than their 

 1 Leminermauu in Forschungsberichten Biol. Stat. Plon. vii, 1898, p. 29. 



