Lecture VI — 90— Mycotrophy 



individual composts or produced in the soil as the result of fungal 

 action. The chief biological change in relation to fertility of the soil 

 is production of toxins, according to Brian (1945), especially of 

 "fungistatic organic substances" produced by Penicillia. The chief 

 toxin appears to be gliotoxin, which has been found highly toxic to 

 mycorrhizal fungi. Brian suggests that the toxicity of Wareham soil 

 may be due to accumulation of gliotoxin and other antibiotic 

 substances. 



Valuable as Dr. Rayner's (1944) studies on the Wareham area 

 undoubtedly are, the results will of course be applied with caution to 

 other areas. Results obtained with a very unusual soil existing at low 

 altitude but high latitude under an oceanic climate will not necessarily 

 be applicable to all other areas. As evidence in point, the paper by 

 LiNDQUiST (1945) may be cited, in which it is stated that "larger and 

 better-colored seedlings" of Pinus resin osa were grown on a duff-peat 

 mixture than on a compost-peat area. Again, composting often pro- 

 duced abnormally crooked roots (Muntz, 1945). 



A study of the organic matter of forest soils led Romell (1938) 

 tO' a new theory of mycotrophy. In experimental work in a spruce 

 forest in Sweden he sank sheet-iron shielding, one foot high, in a poor 

 stand of spruce, surrounding two quarter-hectare plots. One plot, 

 being covered with blueberry bushes, was mowed with the scythe while 

 the other plot was untreated. The author states that a marked efifect 

 resulted, for the vegetation on the plots became thriftier and greener, 

 and retained its foliage longer in autumn. Romell considered the 

 effect due to killing of the tree roots or of mycorrhizae and their 

 associated fungi by trenching, the organic matter thus killed becoming 

 "green manure" for the remaining vegetation. Also, root competition 

 of the trees, and fungal competition, was stopped. Numerous sporo- 

 phores of the supposed mycorrhizal fungi were formed outside the 

 plots while practically none were formed within. Romell thought 

 that these experiments show a fundamental physiological difference 

 between litter-decomposing and mycorrhizal fungi, the latter being 

 practically unable to break down dead organic residues under condi- 

 tions prevailing in nature. He points out the value of trenching experi- 

 ments in mycotrophic studies, since laboratory experiments show 

 merely what is physiologically possible but not what is ecologically 

 important. 



