40 



MISSOURI BOTANICAL GARDEN. 



Closterium stri^osum Breb. Arboretum pond. 



Mar., 



. Rather common. 

 Cosmarium Botrytis Menegh 

 Cosmarium Broomei Thwaite.* 



* 



Cosmarium granatum Breb. Nymphaea pool. Apr., May. 

 Cosmarium margaritiferum Menegh.* 

 Cosmarium Phaseolus var. minor Boldt. Nymphaea pool. 

 Mar., May. 



Micrasterias americana (Ehrenb.) Ralfs. Typha angusti- 

 folia pool, with filamentous algae. Rare. May. 



Pleurotaenium Trabecula (Ehrenb.) Nag. West side of 



Lagoon. 



Rocks. Rather common. 



Pleurotaenium Trabecula var. granulata West. West La- 



goon 



Rather common. 



Penium margaritaceum (Ehrenb.) Breb. Nymphaea 

 pool. Rare. May. 



Staurastrum sp. 



ZYGNEMACEAE. 



through 



Spirogyra dubia Kiitz. Nymphaea pooh Abundant. Con- 

 jugating Mar. 15. 



Spirogyra Grevilleana (Hass.) Kiitz. Fountain pond. 

 Waterfall stream. Rather common. Sept. and 

 May. Conjugating early in Mar. 



Spirogyra longata (Vauch.) Kiitz. Waterfall stream. 

 Fountain pond. September and through May. The mate- 

 rial in the garden does not exactly conform to the type de- 

 scription. There is, however, observed a variation in the 

 measurements given for the vegetative cells as described by 

 Collins, who gives 20-36/x as diameter; Petit 25-30/*; 

 De Toni, 24-30/*. There is also more or less variation in 



regard to the length of the cells in descriptions. Collins de- 

 scribes the spore as broadly ovoid; Wolle, twice as long as 

 broad, though all state that the spore completely fills the 

 diameter of the cell without swelling, which is true in this 

 case, whatever may be the width of the filament. The mea- 

 . surements of the garden specimens are: veg. fil. 21. 4-28.8 jx : 

 chromatophore up to 6.4 /x with as many as 5 coils. The 

 vegetative cells are up to 10 diameters long, usually less; 



