Surveying generally the field covered in this chapter, one can only be impressed with the fragmentary character of our knowledge and with the fact that, owing to the selective nature of the technique, the data we possess, if assumed to be representative, give an entirely partial and erroneous picture of the soil fungi. From the qualitative aspect, the chief impediment is the impossibility of obtaining reliable specific determinations of very many of the soil fungi. Lists of doubtfully-named forms from particular soils or geographic regions are useless or a positive evil, and there is imperative need for the systematising of selected genera by physiological criteria, such as has been partially done for _Penicillium_, _Fusarium_, and _Aspergillus_. Furthermore, until a standardised and non-selective technique has been devised, or a number of standardised selective methods for particular groups, comparative investigations into specific distribution can give little of value. This latter criticism is also very applicable if regard be paid to the quantitative aspect of soil work, for progress here largely depends upon the elaboration of a standardised fractionation technique. Every single factor in these methods needs exact analysis, for each gives opportunity for great error, and each error is magnified many thousand times in the final results. Much has been done in this direction at Rothamsted, but more remains to do. Finally, working with single species in sterilised soil under standardised conditions, there is fundamental work to be done on the relation of plate colony to soil “individual.” [1] Adametz, I., “Untersuchungen über die niederen Pilze der Ackerkrume,” Inaug. Diss., Leipzig, 1886. [2] Brown, P. E., and Halversen, W. V., “Effect of Seasonal Conditions and Soil Treatment on Bacteria and Molds in Soil,” Iowa Agric. Expt. Sta. 1921, Res. Bull., 56. [3] Coleman, D. A., “Environmental Factors Influencing the Activity of Soil Fungi,” Soil Sci., 1916, v., 2. [4] Conn, H. J., “The Microscopic Study of Bacteria and Fungi in Soil,” N.Y. Agric. Expt. Sta., 1918, Bull. 64. [5] Dale, E., (_a_) “On the Fungi of the Soil,” Ann. Mycol., 1912, 10; (_b_) “On the Fungi of the Soil,” Ann. Mycol., 1914, 12. [6] Fischer, H., “Bakteriologisch-chemische Untersuchungen; Bakteriologischen Teil,” Landw. Jahrb., 1909, 38. [7] Goddard, H. M., “Can Fungi living in Agricultural Soil Assimilate Free Nitrogen?” Bot. Gaz., 1913, 56. [8] Hagem, O., (_a_) “Untersuchungen über Norwegische Mucorineen I., Vidensk. Selsk, I.,” Math. Naturw. Klasse, 1907, 7; (_b_) “Untersuchungen über Norwegische Mucorineen II., Vidensk. Selsk. I.,” Math. Naturw. Klasse, 1910, 10. [9] Jensen, C. N., “Fungus Flora of the Soil,” N.Y. (Cornell) Agric. Expt. Sta., 1912, Bull. 315. [10] Jones, D. H., and Murdock, F. G., “Quantitative and Qualitative Bacterial Analysis of Soil Samples taken in Fall of 1918,” Soil Sci., 1919, 8.