1919] 



MOORE AND KARRER — A SUBTERRANEAN ALGAL FLORA 



283 



the two types of soil seemed to be determined by the moisture 

 content and the mineral nutrient content- 



Coming to the question of the presence of algae underground, 

 Esmarch continued to attempt to correlate their growth with 

 different types of soil. Samples were taken at about the same 

 place as those used for surface cultures, at a depth usually of 

 from 10 to 25 cm. A few, however, extended from 30 to 50 cm. 



below the surface 



samDles were obtained in a manner 



prevent surface contamination. The results are grouped ac- 

 cording to the kind of soil. In tilled land 13 cultures were made 

 from sandy soil, 12 from clay, and 20 from marshy soil. Only 

 5 of these contained no blue-green algae and were from places 

 where there were no surface forms. In all, 18 separate species 

 were found and the number decreased as we went deeper into 

 the soil. In the meadow land 23 out of 32 cultures contained 

 blue-greens, with 15 species represented, all these occurring on 

 the surface as well as underground. In moist sand practically 



*es gave results, with 20 different species showing growth. 

 The brown heath and bog soils produced no blue-greens from 



below the surface. 



Esmarch records the occurrence of these subterranean forms 

 as due to the distribution of surface organisms by seepage of sur- 



face waters or by being carried down by earth worms and other 

 soil organisms, and, although he was inclined to believe that the 

 blue-greens found by him beneath the surface could grow in the 

 absence of light, he does not regard the work of other invest i- 



this subject as being altogether 



more, Esmarch doubts that the blue-green 

 considerable depths in the soil have been able 



lclusive. Further 

 filaments found a 



time 



order to demonstrate this, he 



pared cultures in Petri dishes containing 7-8 mm. of e 

 which a niece of filter-paper was placed with certain blue 



on 



on the surface. Tx 

 1 cm. of soil, the c 

 covered with black 



proof case. 

 20° C. After 



e filter-paper was then covered with about 



altures moistened with distilled water and 



paper, the whole being placed in a light- 



The temperature was maintained at from 15 to 



shorter time, depend 



the 



