ALGAL FLORA OF THE MISSOURI BOTANICAL GARDEN. 29 



water (city water derived from the Mississippi) enters at 

 two points, the fountain in the center of the pond and a pipe 

 at the south side. The level is fairly constant except in 

 rainy weather, when it is variable. The water as it enters 

 the pond maintains a fairly constant temperature, varying 

 slowly through the year, the temperature being practically 

 the same as that of the earth at four feet. It is covered in 

 the winter with a coat of ice for about two months. The algae 

 here group themselves into free swimming, those attached 

 to water plants such as Nymphaea and Potamogeton (sta- 

 tionary) or attached to Azolla (floating). The free floating 

 groups are swept across the surface of the pond by winds 

 and in overflows after rains are swept down the stream. 



Of the algae listed for this habitat, Bulbochaete, the Spiro- 

 gyras, Mougeotia, Palmodictyon, Cladophora, and Oedogo* 

 nium were at some stage attached. The others were floating 

 or free swimming. Pleodorina was always found in warm, 

 shallow water near the edge of the pond in a tangle of fila- 

 mentous algae and small water plants as was generally true 

 of the Volvocaceae in this pond. This piece of water con- 

 tains several Spirogyras, only three of which have been de- 

 termined, since conjugation had not taken place. All the 

 filamentous forms are more or less closely associated in 

 masses, Spirogyra and Oedogonium being predominant. 



Typha angusti folia pool. This pool at the edge of the 

 Fountain pond is about 4x6 ft. in size and seldom contains 

 more than five inches of water, usually about two inches, and 

 is often muddy without standing water. It contains a thick 

 growth of Typha angustifolia. Observations were not taken 

 here until March when an interesting association was found. 



Mougeotia scalaiis, Spirogyra tenuissima and Oonatonema 

 sp. formed a closely interwoven mass in the spaces of which 

 were several species of Cosmarium, Closterium and one of 

 Micrasterias. 



Waterfall stream. This stream connecting the Fountain 

 pond and Lagoon contains fourteen waterfalls, all of which 

 have limestone surfaces with the exception of X and XII, 



whose surfaces are cement covered. 



