LECTURE Vin 

 MYCODOMATIA 



Significance of the Term: — Literally, the word "mycodomatium" 

 means "fungus-chamber". Frank (1891) said that on the basis of 

 nutritional physiology, endotrophic mycorrhizae and root nodules may 

 be considered together : their morphological differences will be taken 

 care of if we call one "endotrophic mycorrhizae" while nodules of 

 alder and legumes are called "Pilzkammer" or mycodomatia. But as 

 nodules of legumes contain bacteria rather than fungi, we prefer to 

 limit the term mycodomatia to those hypertrophied structures found 

 on Alnus and a number of other plants which are caused in whole or 

 in part by fungi. In using the word "mycodomatium" in the essential 

 sense given it by Frank, we realize that we are not following the 

 original meaning as used by Lundstrom in 1887. Melin (1936) 

 has revived the term in its proper sense and applied it to all myco- 

 trophic structures, those in which the symbionts "in einem Verhaltnis 

 gegenseitiger Forderung stehen". Perhaps we should follow Melin's 

 lead, but we encounter two difficulties: {1) It is very uncertain that 

 all — or any — of the mycotrophic symbioses are true mutualisms, and 

 it would be extremely hard to sort them out in classes of mutualist 

 and non-mutualist. (2) If we gave up the word "mycodomatium", 

 we would have no term to apply to those hypertrophied structures 

 known as nodules, excrescenses, tubers, tubercles, etc. The term "my- 

 cocecidium" has been applied to them, but this term refers to galls and 

 is generally understood to refer to a parasitic structure. Perhaps 

 Frank's "Pilzkammer" should be the term used !* 



All leguminous nodules caused by bacteria are ruled out of our 

 study. Known from the days of duHamel duMonceau in the middle 

 of the 18th century, nodules of legumes have attracted much attention 

 and their nutritional processes are of related interest to those of my- 

 codomatia. It is true that endophytic infection of leguminous roots 

 is widespread but vesicular-arbuscular mycorrhizae are not nodules. 



In the present state of our knowledge it is impossible to state 

 positively the exact character of mycodomatia ; but it is evident that — 

 regardless of how they are formed — ^they are outgrowths of a larger 

 sort than mycorrhizae. The latter are swollen side-branches ("short- 



*Baas Becking has called attention to the mistake of making a false analogy 

 between symbiosis in leguminous nodules and the symbioses occurring in leaf- 

 nodules and mycorrhizae {cf. Naturwet. Tijdschr. v. Nederl. Ind. 102:120, 

 1946). 



