WISCONSIN PHYTOPLANKTON 19 



KEY TO THE SPECIES. 



Protuberances with simple spines (1) ^- d^c^^^ 



Protuberances with emarginate verrucae (2) T. vertieillatum 



1. Triploceras gracele Bailey. PI. 55, Figs. 5-6. 



Smithsonian Cont. to Knowl. 2, Art. 8: 38, pi. 1, fig. 10. 1851 (sep) ; G. S. West, 

 Jour. Linn. Sic. Bot. 39: 54, text figs. 7A-7B. 1909. 



CeUs large, length 12-20 times the breadth; median constriction 

 fairly well defined; semicells cylindrical, somewhat attenuated at 

 poles, without line of lateral margins strongly undulate, undulate 

 outline caused by transverse whorls of mamillate protuberances that 

 terminate in acute, horizontally disposed, spinate verrucae in inferior 

 portion of semicell and upwardly disposed spinate verrucae m supe- 

 rior portion ; semicell apices flattened and with two fairly long, diver- 

 gent, obliquely disposed, truncate processes terminating in two or 

 three short spines; apex also with a single (rarely two) mamillate 

 protuberance arising midway between the bases of the polar processes 

 and terminating in an acute erect spine. Vertical view of pole elliptic, 

 with poles terminating in spines and each lateral margin with a 

 single, alternately disposed, truncate process. Cell wall without pores. 

 Chloroplast axial, with 6-8 straight delicate longitudinal ridges ex- 

 tending from semicell base to apex; pyrenoids fairly numerous and 

 forming an axial row. (Tychoplanktont.) 



Zygospores unknown. 



Cells 368-550)11 long; 27.5-31.5 /^ broad at basal whorl (with ver- 

 rucae), 18-25 /x broad at apical whorl (with verrucae), and 10-12.5 ft 

 broad just above apical whorl. Distance between ends of apical 

 processes 30-36 jx. 



Crooked (rrr), Devils (rrr), Jag (rrr). Little Doctor (rrr), Eudolph (rrr). 



The great variability of this species is well known and there has 

 always been a conflict of opinion as to the limits of variation in the 

 type. G. S. West's discussion of the type and its varieties is so thor- 

 oughgoing that further remarks are superfluous. 



2. Triploceras verticillatum Bailey. PI. 55, Figs. 7-9. 



Smithsonian Cont. to Knowl. 2, Art. 8: 37, pi. 1, fig. 9. 1851 (sep.). 



Docidium verticillatum Bailey, in Ralfs, Brit. Desm. 218, pi. 35, figs. 9A-9E. 

 1848; Wolle, Freshw. Algae of U. S. 27, pi. 61, fig. 18. 1887. 



Cells large, stouter than the preceding species, length 8-12 times 

 the breadth, median constriction well defined; semicells cylindrical, 

 somewhat attenuated towards the poles, with outline of lateral mar- 

 gins strongly undulate, with 12-22 transverse whorls of mamillate 

 protuberances that terminate in broad emarginate verrucae (tri- 

 angular in front view), protuberances in superior portion of semicell 

 at times terminating in simple spines; apices truncate, with two 

 long, divergent, obliquely disposed processes that terminate in two 

 long spines ; semicells apices also with a mamillate protuberance bear- 

 ing two erect spines that lies midway between the bases of the apical 



