Lecture VI — 69 — Environment 



Eberswalder Kiefernbodens" ; and Sarauw (1904), after reviewing 

 the evidence, said that in general : "la formation des mycorhizes n'est 

 influencee que d'une maniere quantitative et non qualitative par les 

 differentes sortes de sols." But Prat (1926), in a study of Taxus, 

 concluded that the nature of the soil seems to exercise an influence 

 on branching of the roots. Harley (1937) agrees in that he says 

 the form of mycorrhizae in beech and extent of infection is correlated 

 with soil type. Kelley (1941) studied mycorrhizae of Pinus vir- 

 giniana in four soil series, — Chester (granitic), Conowingo (serpen- 

 tine), Dekalb (sandstone), and Sassafras (Cretaceous gravel); and 

 he found characteristic differences in each of the soil series. The my- 

 corrhizae were coral-branched in sandy soils and racemose or elongate 

 in clay soils, while pseudomycorrhizae predominated in wet clay soils. 

 In droughty sands were found necklace-beaded mycorrhizae, caused 

 by intermittent growth. A. Moller is said to have found different 

 sorts of mycorrhizae in different soils about Berlin (Henry, 1903). 



Frank had supposed that mycorrhizae are found only on humus 

 soils but are absent from sands and sandy soils. Moller (1902) 

 thought, on the contrary, that pines produced mycorrhizae in sand 

 rather than in humus. In France, Vuillemin (1890) "a constate aussi 

 que le terre sabloneuse de bruyeres est favorable aux mycorhizes." 

 Pessin (1928) records pine mycorrhizae from Norfolk sandy loams 

 and Orangeburg fine sandy loam in the southern U.S.A. 



Calcareous soils are usually considered unavailable to mycotrophic 

 plants since most mycorrhizal fungi prefer an acid substratum. But 

 Calhina is rather an anomaly since it grows on chalk downs which are 

 rich in mineral constituents but poor in lime. Rayner ( 1921 ) found 

 that the mycorrhizal fungus grew well even in a strongly alkaline 

 extract of pH 8.0; but Calluna developed normally in presence of 

 fungus (but with exclusion of bacteria) only on Ca-poor soils. 

 RuGGiERi (1937) found almond mycorrhizal on calcareous soils of 

 Sicily. Pine does not thrive on alkaline soils, and it is possible that 

 some of the difficulty with establishment of pine on prairie soils may 

 have been due to the alkalinity of the limestone soils of the region. 

 Young (1938) corrected alkalinity in nursery beds by S applications. 



Solfatara soils of volcanic regions present special conditions. 

 MiEHE (1918) had drawn attention to the fact that mycotrophic and 

 bacteriophagic plants occur in numbers on solfatara soils, and sup- 

 posed that they were excellent pioneers inasmuch as they are able 

 to fix atmospheric N. Faber (1925) came to the same conclusion: 

 he said that these soils are characterized by Al-content, N-poverty, 

 acid content, and high temperature ; and that solfatara plants are 

 adapted to these factors. He found both xeromorphic and hygromor- 



