Lecture VIII — 107 — Mycodomatia 



seen connecting adjacent "masses" through cell-walls, tangentially. 

 The cell nucleus is not hypertrophied. Rosette formation by Actino- 

 myces is mentioned by Youngken in a study published in 1915 on 

 the Myricaceae ; and he said that this organism later penetrates 

 tracheae and grows out into the seed. In "M. cerifera," Harsh berger 

 (1903) described mycodomatia inhabited by Frankia. He supposed 

 that these structures were intermediate between ectotrophic mycor- 

 rhizae as in Monotropa and endotrophic forms as in Thismia. 



Alnus: — In alders occur the earliest described root excrescences 

 which may be termed mycodomatia. Meyen in 1829 gave the first 

 description of tubercles in alder (so far as we are aware), and con- 

 sidered them as "pseudomorphosed roots" in the ends of which there is 

 a parasitic growth comparable to that of Lathrea, etc. Meyen was sure 

 that he had shown them to be "ganz vollkommene parasitische Ge- 

 bilde" and that they were formed by "gleich anderen vollkommenen 

 Organismen". Since then there have been numerous other descrip- 

 tions given but their exact nature and symbionts still remain unsettled. 

 Apparently alder nodules are not caused by one organism nor do they 

 always have the same physiology, for some investigators describe 

 them as bacterial, others as fungal. Thus Cernik (1937) lists the 

 "fungi" of alder nodules as Frankia, Schinsia, and Actinomyces, all 

 of which are presumably bacterial; while Pieschel (1929) cites 

 Lactarius lilacinus and L. cyathula as always associated with alder 

 and presumably the mycodomatial symbionts, with Gyrodon rubescens 

 a probable third symbiont. Two investigators report synthetic my- 

 codomatia for alder, — Plotho (1941) and Roberg (1938). Roberg 

 grew seedlings of four species of alder in a synthetic nutrient solution 

 with a suspension of ground root-nodules isolated from each of the 

 species. Only healthy seedlings reacted to inoculation by nodule 

 production; and in all cases the symbiont was Actinomyces alni. Be- 

 cause of the frequent presence of this organism, Shibata (1902) 

 termed the alder mycodomatia cases of vegetable actinomycoses. 



A number of papers describe nutritional processes of alder my- 

 codomatia. Shibata, already mentioned, tells of the "blaschen" or 

 small bodies formed by the "fungus" in mycodomatial cells and their 

 subsequent digestion ; he also described clots which contained, besides 

 some fungal hyphae, a number of little rounded drop-like or oval 

 structures which he termed "sekretkorper". But Zach (1908) did 

 not find these bodies in A. glutinosa (Shibata worked with A. 

 japonica), but considered the broken threads or "Stabchen" of Shi- 

 bata as concentrated cell-content of the hyphae while spore-like knots 

 and bacteria-like threads are degenerate forms of hyphae which, he 



