156 WISCONSIN PHYTOPLANKTON 



SCENEDESMUS LONGUS Meyen. PI. 39, Figs. 20-22. 



Nova Acta Phys.-Med. Acad. Caes. Leop. Nat. Cur. 14: 774, pi. 43, fig. 28. 

 1829. G. M. Smith, Trans. Wis. Acad. Sci., Arts, & Lett. 18 2 : 469, pi. 31, figs. 

 156-158. 1916. 



Scenedesmus quadricauda var. setosus (Kirchner) Lagerheim, Ofvers. Kgl. 

 Sv. Vet.-Ak. Fort. 39, No. 2: 63. 1882. 



Coenobe flat, of 2-48 (generally 4) cells arranged in a single linear 

 series. Cells ovoid to oblong-cylindrical, with rounded poles. Poles 

 of all cells with 1-2 spines. Cell wall destitute of spines except at the 

 poles. ( Tychoplanktont) . 



Cells 4-5 p. broad, 8-11 ju. long. 4-celled coenobia 8-11 /x broad, 16- 

 20 p. long. 



Rock (rr). 



var. Naegelii (Brebisson) comb. nov. PI. 40, Figs. 1-2. 



Scenedesmus Naegelii de Brebisson, Mem. de la soc. Imp. de Sc. Nat. de 

 Cherbourg 4: 158. 1856. 



Scenedesmus caudatus Nageli non Corda, Gatt. einz. Algen 91, pi. 5, figs. 

 2c-2d. 1849. 



Colonies flat, always eight-celled. Cells cylindrical, with rounded 

 poles. Terminal cells with spines at both poles, interior cells with 

 spines at one pole, rarely at both poles. (Facultative Planktont). 



Cells 6.6-11 p broad, 18-33 /x long. 8-celled colonies 18-33 fj. broad, 

 50-85 /x long. 



Blake (rr), Camp (rrr), Poor Farm (rrr), White Ash (rr). 



This alga was described by de Brebisson from the drawings of 

 8. quadricauda by Nageli. In my monograph of Scenedesmus I in- 

 cluded it as a synonym of 8. longus (Trans. Wis. Acad. Sci., Arts, & 

 Lett. 18 2 : 469. 1916) but am now convinced that it should be con- 

 sidered a distinct variety. The cells are much larger than the typical 

 form but unfortunately Nageli gives neither measurements for the cells 

 nor an indication of the scale of magnification of his drawings. The 

 measurements stated above are those of cells from Wisconsin lakes. 

 The peculiar arrangement of the spines that Nageli figures, where three 

 adjacent interior cells have spines on the same end and none on the 

 other with the reverse condition in the remaining interior cells, was 

 found to be a common but not a constant character since specimens were 

 found with spines at both poles of interior cells. 



