64 WISCONSIN PHYTOPLANKTON 



Clare (ss), Crawling Stone (rrr), Des Moines (cc), Diamond (ss), Duck (rr), 

 Dummy (rr), Dutchmans (ss), Fish (ss), Fowler (sss), Grindstone (rr), 

 Half Moon (ss), Horseshoe (1) (ss), Horseshoe (2) (rr), Howey (rr), Island 

 (BS), Jennie (rr), Kegonsa (aa), Kimball (rr), Lac Court Oreilles (ss), Lake 

 of the Woods (r), Lindy (rr), Long (1) (sss), Loon (r), Mendota (s), Monona 

 (cc), Nancy (ss), North Twin (r), Mercer (rrr), Middle McKenzie (ss), Mud 

 (3) (aa), Oconomowoc (rr), Owen (rrr), Razorback (aa), Reserve (rr), St. 

 Croix (rr), Sand (1) (rr), Sand (3) (rr), Shell (rr), Soft (rr), Trout (cc), 

 Waubesa (cc), Whitefish (sss), Wild Goose (rr), Winnebago (r). 



A bloom of this alga can be recognized at once by the minute seed-like 

 colonies surrounded by an aureole of whitish threads. It was first 

 noted by Davis in England in 1804 and the plant figured and described 

 by Smith in his English Botany. The various references to the alga 

 before the recognition of a definite plankton flora have been compiled 

 by Bornet and Flahault as well as P. Richter. Since the study of the 

 plankton flora by phycologists the alga has been found in the lakes of 

 most European countries. Although there seems to be but a single 

 species of the Rivulariaceae found free-floating in lakes and ponds the 

 nomenclatorial treatment of this species is quite varied. Bornet and 

 Flahault affirm that it is the common Gloeotrichia pisum, which ordi- 

 narily grows attached to submerged plants along the shore, that has 

 broken away and become free-floating. They hold that Rivularia 

 echinulata J. E. Smith (whose dimensions are the same as those of 

 G. pisum) is nothing but a free-floating G. pisum. In my observations 

 on the algae of our lakes there is no correlation between the appearance 

 of G. pisum and G. echinulata in the same lake in Wisconsin. In the 

 region of Madison, G. pisum does not appear until the middle of July 

 and yet at one time there was a heavy bloom of G. echinulata, on the 

 28th of June, a time when there was no G. pisum along the shore. I 

 am convinced that the sessile Gloeotrichia is not the one found in the 

 plankton and that Richter is quite right in reviving the old specific 

 name echinulata. Some investigators hold that Gloeotrichia is but a 

 sub-genus of Rivularia, but I have followed Bornet and Flahault in 

 considering the two distinct. This distinction is based upon the occur- 

 rence of spores in Gloeotrichia and a lack of spores in Rivularia. 



