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2»J ANNALS OF THE MISSOURI BOTANICAL GARDEN 



that only samples from the surface were used, and with a single 

 exception any reference in the literature to soil algae may be 

 regarded as having only to do with those forms which grow at or 

 near the surface. Esmarch, 1 however, in a rather extensive 

 paper, attempted to indicate not only the distribution of Cyano- 

 phyceae upon the surface of various soils but also their occur- 

 rence underground. His method was to use Petri dishes about 

 2 cm. deep, into which 1 cm. of the soil to be studied was intro- 

 duced. The soil was moistened with sterile water and a piece 

 of filter-paper placed over the surface. The cultures were kept 

 in the greenhouse with diffuse light at a temperature of from 

 20 to 25° C, and after periods of from two days to two months 

 growth appeared through the filter-paper. 



In investigating the distribution of blue-green algae on surface 

 soils an attempt was made to determine whether cultivation 

 influenced their distribution. Accordingly, 4 types of uncul- 

 tivated soils, including sandy meadow, marshy bog, forest 

 humus, and moist sand, were investigated. On the sandy 

 meadow, which contained traces of humus, but 3 out of 34 

 samples collected showed the presence of Cyanophyceae on the 

 surface. On the marshy bog soil, after a period of three months, 



of the 35 cultures showed any blue-green algae, although 



few diatoms and 



Both the 



forest humus and the moist sand gave good results, so far as 

 indicating the presence of numerous blue-greens on the surface. 

 In cultivated soils, 3 types were used, namely, sandy, clay, and 

 marshy. Of these, 29 out of 45 samples of sandy soil contained 

 Cyanophyceae, comprising some 12 different kinds. On the 

 clay soil, 35 out of 37 samples proc.uced blue-green algae with 

 23 species. On the marshy soil, of the 40 cultures all but 2 

 showed growth, 22 species being found. While, in general, the 

 above increase indicates that a greater number of blue-greens 

 were found on cultivated than uncultivated soils, the number 

 of samples was so few and taken from such a limited area that 

 no very exact conclusions could be drawn. Any difference in 



1 Esmarch, F. Untersuehungen iiber die Verbreitung der Cyanophyceen auf und 

 in verscheidenen Boden. Hedwigia 55: 224-27o. 1914. 



