CATALOGUE OF PLANTS. 613 



S. acutus, Meyen. 



Same habitat. 

 S. obtusus, Meyen. 



Same habitat. 



OPHIOOYTIUM, Nseg. 

 O. cochleare, A. Br. 



Frequent in stagnant ponds. 

 O. capitatum, Wolle. 



Same habitat. 



CHARACIUM, A. Br. 



C. sessile, Herm. 



Sussex : Cranberry Pond, on algae. 



PROTOOOCOUS, Ag. 

 P. viridis, Ag. 



Everywhere common on the shaded side of trees, houses, 

 rocks, etc. Mr. Wolle reoognizes a large number of aerial and 

 aquatic forms as varieties of this species. 



POLYEDRIUM, Nceg. 

 P. trigonum, Nseg. 

 P. gig&s, Wittr. 

 P. enorme (Kalfs.), Kab. 



All found in ponds. 



PALMELLACE.E. 

 DICTYOSPHuERIUM, Nseg. 



D. Ehrenbergianum, Naeg. 



In ponds ; frequent. 

 D. reniforme, Bulnh. 



Same habitat ; occasional. 

 D. Hitchcockii, Wolle. 



Morris : Frequent in Denmark and Split Rock Ponds. 



