Lecture X —147— Obligate Symbiosis 



point. To illustrate them one may cite the following : A frog is killed 

 and the heart bathed in an isotonic salt solution. One may now say 

 the frog is not dead because its heart is still beating. In regard to 

 Obligate Mycotrophy, there is an academic view of obligatism by 

 which we have to admit that no plant is so united to its fungal partner 

 that the plant cannot be forced to hve in some other way ; and there is 

 a natural view of obligatism by which we perceive that the vast 

 majority of plants in nature are obligatorily mycotrophic through 

 their physiological requirements in a limited environment. 



Added evidence for this view is afforded by the work of Dominik 

 and Jagodzinski (Diary Trees & Forest Res. Inst. Kornik. 1 :48-73, 

 1946). Working with fruit trees, they find that certain spp. are con- 

 fined to a mycorrhizal nutrition. Since the soils of Kornik garden 

 contain less than a minimum required for ordinary plant nutrition, 

 plants growing in it are necessarily dependent on fungi for N supply. 



