Lecture VI — 87 — • Environment 



the question of "prairie", commented on Hatches work and remarked 

 that there is some doubt as to whether the greater acquisition of N 

 by the mycorrhizal seedhngs in Hatch's "prairie" soil experiment 

 is related solely with the more efficient absorption of nitrates and his 

 claim that peptone and nucleic acid can be absorbed directly by the 

 roots of pine seedlings is not discussed from this point of view. In a 

 paper by McComb (1938, also' 1943) the claim is made, based on 

 experimental data, that differences in pine seedling development in a 

 forest tree nursery on old agricultural land in the prairie province 

 (Iowa) are due to disparities in the amounts of available P, and that 

 mycorrhizae are the means of enabling the seedlings to absorb this 

 element at a sufficiently rapid rate for normal growth. Thus Hatch 

 and McCoMB stress P but a writer in the Annual Report of the 

 Wisconsin Agricultural Experiment Station (1942) said that inocula- 

 tion of evergreen seedlings with suitable mycorrhizal fungi, particu- 

 larly Boletus feUeiis, greatly improved growth and survival on prairie 

 soil. The evidence obtained indicated that the mycorrhizal fungi 

 rendered the K present in the soil more readily available to the 

 seedlings. 



That mycorrhizal fungi are absent from at least certain prairie 

 soils is asserted by Rosendahl & Wilde (1942), who found such 

 fungi in cut-over forest lands of central Wisconsin but "invariably 

 absent" from adjacent prairie soils. McComb & Loomis (1944) also 

 report a sharp difference in microflora between forest and prairie soils. 

 Harvey (1908) asserts an absence of fungi from prairies; yet it must 

 be noted that Pfeiffer (1914) found Thisniia mycorrhizal on the 

 prairies at Chicago; and Wilkins & Patrick (1938) presented a 

 paper on the fungi found in grasslands about Oxford. White (1941) 

 regarded mycorrhizal fungi as beneficial, and suggested that mycor- 

 rhizae exert a specific growth-promoting effect upon forest seedlings, 

 the absence of this stimulus being a major factor in the poor growth 

 of trees on mycorrhiza-free prairie soils. But the majority of cases 

 of poor growth of pine in the U.S.A. are apparently not associated 

 with mycorrhizal deficiency (Latham, Doak & Wright, 1939) ; and 

 in Indiana a failure that was so associated was more easily corrected 

 by fertiliser than by inoculation. "Even in new conifer nurseries in 

 the Prairie States growth is usually satisfactory . . ." Again, it must 

 be noted that Jones (1924) said of endotrophic fungi of legumes in 

 western America that no field, no matter how recently reclaimed, is 

 free from infestation and that but few mature leguminous plants are 

 uninvaded by mycorrhizal fungi. 



A great difficulty with the question of occurrence of mycorrhizal 

 fungi in prairie soils is, that the subject has never been investigated. 



