94 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



the cap-like end of the cell ; in some species germinating di- 

 rectly at the summit of the mother cell, in others entirely inde- 

 pendently. 



Not uncommon among other algae, especially the unattached 

 forms ; but seldom found in large quantity. The present treat- 

 ment of this genus follows Lemmerman, 1899, including Scia- 

 dium, generally kept distinct on account of the new generation 

 developing at the summit of the older cell ; but as this same 

 development is found in varieties of some species of Ophiocvtium, 

 in the older sense, the distinction cannot be kept up. 



KEY TO THE SPECIES OF OPHIOCYTIUM. 



i. Attached. 2. 



i. Free. 3. 



2. Cells 5-7 ^ diain., stipe 10-14 /x long. 6. O. gracilipes. 



2. Cells 3-5 M diain., stipe 2-3.5 M long. 5. O. arbuscula. 



3. Bearing a stipe or spine. 4. 



3. Both ends rounded or truncate. 4. O. parrulum. 



4. Stipe with capitate end. i. O.majus. 



4. Stipe or spine acute. 5. 



5. Spine at one end. 2. O. cochleare. 



5. Spines at both ends. 3. O. capitatum. 



1. O. MAJUS Nageli, 1848, p. 89, PI. IV. A, fig. 2; ^em- 

 merman, 1899, p. 29; Phyk. Univ., No. 19, b. Cells solitary, 

 8-17 fj- diarn., spiral or curved in S-form ; at one end with a 

 straight or curved stipe with capitate end ; cells often with hya- 

 line or yellowish oil globules. Fig. 2. Mass. Europe. 



2. O. COCHLEARE (Eichwald) A. Braun, 1855, p. 54 ; Wolle, 

 1887, p. 175, PL CLVIII, figs. 8-14; Lemmerman, 1899, p. 30, 

 PL III, figs. 10-12; P. B.-A., No. 1424. Cells solitary, 5-8 /x 

 diam., arched or spirally twisted, bearing at one end an acute 

 spine i- 1 2 p long. Me., Mass. Europe. 



3. O. CAPITATUM Wolle, 1887, p. 176, PI. CLVIII, figs. 

 3-7 ; Lemnierman, 1899, p. 31, PI. IV, figs. 16-18. Cells soli- 

 tary, 5-10 /Jt- diam., arched, S-curved or spiral, with an acute 

 spine 5-7 M long at each usually swollen end. Mass., N. Y. 



4. O. PARVULUM (Perty) A. Braun, 1855, p. 55 ; Wolle, 

 1877, p. 176; Lemmerman, 1899, p. 33, PI. IV, figs. 31-33; 

 Rabenhorst, Algen, Nos. 516, 1546. Cells solitary, 3-9 /u, diam., 

 straight, arched or spiral, rounded at each end. Greenland, 

 Me., Mass., N. Y. Europe. 



Yar. CIRCINATUM (Wolle) Lemmermau, 1899, p. 34, figs. 

 15-18; O. circinatnm Wolle, 1887, p. 176, PI. CLVIII, figs. 



