The WorJclng of the Madisoyi Lakes. 



125 



pisum. Each consists of a mass of tapering threads arranged radially in a 

 gelatinous matrix, from the surface of which their apices protrude more 

 or less, often rendering the surface bristling. The base of each filament is 

 occupied by a heterocyst, followed by a slender cylindrical spore, above 

 which come a series of vegetative cells gradually decreasing in diameter, 

 until they form a slender colorless point. 



This species has been reported from time to time in Europe, 

 under a number of names, and has recently been discussed at 

 some length by Bornet and Flatanet. According to Arthur, 

 who studied a sterile form occurring in certain Minnesota 

 lakes, it is believed to be jjoisonous to cattle that drink the 

 water containing it. Usually it is found without spores, but, 

 as I learn from M. Bomet, it can readily be kept in the aqua- 

 rium for several months, during which time the sterile forms 

 usually produce spores. 



Frequenters of the seashore are familiar with a sHme of a 



bright peach-color that is abundant in midsummer in and 



about stagnant pools in salt marshes. This is of the same 



nature as the scums already referred to, and is caused by 



what is generally called Clathrocystis roseo-persicina, a plant 



related to the chroococcaceae, but destitute of chlorophyll, 



and recently transferred to the bacteria, and placed under the 



genus Bcggiatoa, by Zopf. Species of Trichodesmium, Spiru- 



lina, Lyngbya, Oscillaria^ etc., which iisually grow at first on B 



the bottom, frequently break free and float in a gelatinous 



film of a yellowish, blue-green, violet or reddish color; and 



diffiused tlu-eads of some of the species of these genera more 



rarely form a true water-bloom- Limnoclilide flos aquce is also 



a common Nostochineous species that forms a water-bloom. 



In Europe, water is occasionally fouled, if not discolored, by 



Leptoviituis lacteics, one of the Saproegnicaj, and Crenothrix 



Kuhniana, one of the bacteria closely related to Beggiatoa. 



Beggiatoa alba is also abundant in sulphur springs, hot ditches 



and stagnant bays, but is usually attached to the bottom, float- Gloeotrichia 



, . „ Pisi-M Thiir.— 



ing only exceptionally. Fertile thread, 



Certain species of Peridinium and Euglena, wliich have been ^^ ooU.) 



regarded as infusoria until recently, but are now classed by Klebs with the 



algce, are quite frequent on the water and mud of stagnant ditches, etc. , 



in spring, imparting to it a bright red or green color. A species of the 



1 Tlie largest of these, Oscillaria princeps Vauch, with filaments 50-57 ^w in diameter, is 

 found floating in such masses every season in a brook near the city. 



- 1 have in my herbarium a specimen of Oscillaria (or Beggiatoa), diffusa Farlow, the oscil - 

 lating threads of which, composed of cells 4-3 j:i in diameter and 2-1 j^i long, gave a pro- 

 nounced purjile color to the water of Jamaica Pond, Mass., in the spring of 1884, as I am in- 

 formed by Dr. Farlow. 



