224 PRINCIPLES OF SOIL MICROBIOLOGY 



and varieties of diatoms were found in field and garden soils, 5 in 

 marshy soils, and comparatively few or none at all in forest and heath- 

 land soils. 



Robbins 32 sampled several Colorado soils which were very rich in 

 nitrate, by removing first the loose debris on the surface, then taking 

 samples from the upper 3 to 4 inches. Out of 21 different species 

 recorded, there were 18 Cyanophyceae, 1 diatom, and only 1 unicellular 

 organism belonging to the Chlorophyceae. The Nostococaceae were 

 best represented. The most prevalent species were Phormidiwm tenue, 

 Nostoc sp., Anabaena sp., Nodularia harveyana, and Stigonema sp. 



A distinct subterranean algal flora independent of the nature of the 

 soil and the locality was found by Moore and Karrer. 33 Some species 

 multiplied even when buried at a depth of one meter. In view of the 

 fact that these algae were found in compact undisturbed soil, the pos- 

 sibility suggested itself that algae are present in the soil in a vegetative 

 condition and actually grow there and play a definite function in soil 

 transformations. 



The following list contains the algae found in the soil by Moore and Karrer 

 and the greatest depth at which they occurred: 



Chlorococcum humicola (Nag.) Rab 100 cm. 



Hantzschia amphioxys (Ehr.) Grun 100 cm. 



Navicula atomoides Grun 100 cm. 



Trochiscia ? 80 cm. 



Stichococcus bacillaris Nag 70 cm. 



Oscillaloria amphibia Agardh 70 cm. 



Cladophora sp 60 cm. 



Anabaena sp 20 cm. 



Nitzschia kutzingiana Hilse 20 cm. 



Nostoc muscorum Ag 20 cm. 



Oscillaloria chlorina Kutz 20 cm. 



Oscillatoria sublilissima Kiitz 20 cm. 



Scytonema hofmanni Ag 20 cm. 



Oscillaloria anoema (Kutz) Gomont surface 



Oscillaloria formosa Bory surface 



Oscillatoria splendida Greville surface 



An extensive study of the algal flora of desiccated soils has been made 

 by Bristol. 34 Forty-four samples of soil desiccated from 4 to 26 

 weeks and from widely separated localities were examined; a widely 

 distributed ecological plant formation consisting of moss protonema 



32 Robbins, 1912 (p. 217). 



13 Moore and Karrer, 1919 (p. 217). 



34 Bristol, 1920 (p. 218). 



