Kelley — 88 — Mycotrophy 



There is not a single paper devoted to an analysis of the subject and 

 not a dozen references in the literature. The reputed absence of my- 

 corrhizal fungi from prairie soils is simply a dictum mundi that has 

 been adopted trustfully as an axiom; whereas there are several facts 

 against it. Thus, trees and presumably root fungi have occurred from 

 time immemorial along the numerous watercourses which traverse the 

 prairies ; trees and shrubs flourish along streets of innumerable prairie 

 towns and about tens of thousands of prairie farmsteads. These woody 

 growths have a hard battle against desiccating winds and temperature 

 extremes in the trying climate of the region, but hardier species thrive. 

 It is true that conifers often fail in prairie soils, but it is possible that 

 the failure may be due to alkalinity of the soil, an alkalinity that pos- 

 sibly may be connected with the fact that the prairies are very generally 

 underlaid by limestone, although prairie soils are not residual. And 

 then it must be noted that trees spread rapidly into the prairies when 

 the sod is broken. As to the Plains which lie west of the prairies, 

 aridity is a potent influence on plant development, and establishment 

 of trees in these droughty soils must always be conditioned by the 

 water supply as well as by other "soil factors". 



Soil Inoculation: — On the assumption that necessary mycor- 

 rhizal fungi are absent from certain soils on which trees are to be 

 grown, the practice of soil inoculation with these fungi has arisen. 

 Thus Rayner (1934) found that seedlings which grew poorly on a 

 sterile heath were greatly benefitted by application of humus which 

 "must contain active mycorrhizas of the species free from any ab- 

 normalities of structure and from contaminations of such pseudo- 

 mycorrhizal fungi as can be identified". Probably there were "active 

 mycorrhizas" in the transplants made to various treeless regions in 

 those benighted days before the science of mycorrhiza flamed so 

 brightly. Thus, Leonard Flemming, a pioneer in afforestation in 

 South Africa, says nothing of inoculating the soil when he planted 

 thousands of seedling pines on the high veld where trees had never 

 grown before. It was water that the pine-trees craved and when he 

 supplied their need the trees flourished. But in Australia, exotic 

 conifers needed for softwood plantings in the Brisbane Valley often 

 failed to grow at the Yarraman nursery, and on examination it was 

 found that the roots lacked mycorrhizae (Young, 1938). (In passing 

 it may be remarked that Frank in 1894 had raised the question 

 whether the needful fungi were present in all soils used for planta- 

 tions.) On inoculation of the seed beds with the proper mycorrhizal 

 fungus, mycorrhizae were formed and the seedlings became thrifty. 

 Moreover, it appears to be part of the standard practice to inoculate 



