124 Wisconsin Academy of Sciences, Arts and Letters. 



am informed that though some water-bloom, occurred, and at times be- 

 came offensive, especially in the latter summer, it was less abundant than 

 in 1882. In 1885 but little was seen. Once or twice toward the end of July 

 the scum accumulated in smaU quantity, but was quickly dispersed by a 

 change in the wind, and it was not until nearly the middle of August that 

 I Tvas able to collect specimens. On the 10th of August quite a quantity 

 was noticed floating in sheltered places along- the University shore, and in 

 the lee of Picnic Point, and more was seen off the shore toward Merrill's 

 Springs, where it had stained the rocks somewhat. This consisted entirely 

 of the Anabcena represented in figure 4, in good fruit. 



After a warm spiing, on my return to Madison, June 6, 1887, I observed 

 a considerable quantity of putrid scum on the shore of Fourth Lake, but a 

 south wind scattered it before specimens were obtained. The succeeding- 

 fortnight was hot, and after a couple of calm days, succeeding a strong- 

 wind from the northwest, the southern half of the lake was filled with sus- 

 pended particles about a millimeter in diameter. These consisted exclus- 

 ively of Anabcena hassalUi, already in full fruit, the spores with the cus- 

 tomary Sphaerozyga arrangement, in a collection made June 20th. Subse- 

 quently to this date very little water-bloom was seen, and during the en- 

 tire summer the lake remained unusually free from it until September 7^ 

 when I left the city. 



The water-bloom of 1888 was also slight. Floating specimens collected 

 in the latter half of Aiigust consisted of fruiting plants of the larger Ana- 

 baena, similar to figure 4, with a small quantity of Lynghya nollei. 



The naming of this larger Anaboena has been attended with some diffi- 

 culty. The first specimens collected, which were sterile, were referred to 

 a form of A. flos-aquae; but the subsequent collection of material in fruit 

 has shown that this reference was incorrect, if A. Jios-aquae is understood 

 to be characterized by globose or sub-globose spores,' remote from the 

 heterocysts, and hence referable to the sub-genus Trichormus. It is, how- 

 ever, identical with the Nostoc flos-aquae of Lyngbya of Dr. Bornet's sketch 

 (fig. 1), which would be referred to the sub-genus Sphcerozyga, and agrees 

 essentially with the type of A. hassallii. 1 should, therefore, refer our 

 plant to A. hassalUi. According to Wittrock, this species varies in the 

 relative position of spores and heterocysts as widely as the three figures 

 furnished by Dr. Bornet. Among our Madison specimens, none have been 

 found with the spores remote from the heterocysts, but the spores are not 

 infrequently solitary, as noted by Rabenhorst.- 



About the middle of August 1886, while rowing across Second Lake 

 (Waubesa), south of Madison, my attention was attracted by very numer- 

 ous yellowish-green spherules about 1 mm. in diameter, fioating at all 

 depths in the water. These proved to be small fronds of Glocotrichia 



1 Cf . for example, Cooke: Fresh- Water Algae, p. 235, pi. 93, f. 1. 



2 Rabenhorst: Flora Europsea alg. aq. dulc. et submar. II., 195. 



