Lecture VIII —109— Mycodomatia 



enters tannin cells. The nodules recall those of Casuarina. Fungal in- 

 vasion of Orobus was discovered by Frank (1879), and he figured 

 arbuscles and vesicular swellings in the nodules of O. vermis and 

 O. tuherosus; and Frank considered that the hyphae were trans- 

 formed into "Sproszellchen". 



Ailanthus: — In the Erlangen Botanic Garden, Andreae (1894) 

 found that sturdy side-roots of Ailanthus had irregular tuberous out- 

 growths of 5-40 mm. diameter placed directly on the root cylinder and 

 composed of smaller bodies in a grape-like cluster. Their structure 

 was thought due to the higher plant and not induced by the fungi 

 (mostly Pyrenomycetes) found in the nodules. Further studies are 

 awaited on these structures. 



Geanothus: — Nodules were noted on C. americanus by Beal in 

 1890 and were described by Atkinson (1892). While resembling 

 in form leguminous nodules, he found the causal organism was a 

 "fungus" which he named Frankia ceanothi. Material was collected 

 from Alabama and Michigan, and similar nodules were found on 

 Alnus serrulata. In a more extended study, Arzberger (1910) said 

 that infection is through epidermis or root-hair and the mycodomatium 

 consists of 3 systems of tissues : an outer corky layer, a middle cortical 

 tissue, and an inner vascular bundle. In the cortical layer are infested, 

 hypertrophied cells, the nuclei being enlarged. He noted also three 

 stages in development of the fungus, — mycelial, "sporange" and 

 digested. No "Exkretkorper", as described by Zach, were found, but 

 an enzyme capable of digesting fibrin was found. He said that sym- 

 biosis exists but both host-cell and fungus dies. A very different de- 

 scription was given by Bottomley (1915), who considered the 

 nodules purely bacterial, formed by bacteria of the Bacillus radicicola 

 group. As no nodules were formed on C. americanus in England, he 

 imported material from America, securing nodules also of C. velu- 

 tinus. The bacteria, when isolated, grew in pure culture and fixed N. 



Elaeagnus: — The same discrepancies must be noted in descrip- 

 tions of Elaeagnus nodules. Brunchorst and Frank agreed at first 

 for their fungal nature; then Frank (1887) withdrew to the posi- 

 tion that the nodules are merely reserve organs, containing no sym- 

 biont. Zach (1908) described them as fungal and similar to those of 

 Alnus; Nobbe (1892) believed that he had demonstrated N-fixation 

 with them. On the other hand, Spratt (1912) identified the causal 

 organism as Pseudomonas radicicola, but stated that it does fix free 

 N. The author found coralloid mycorrhizae but no nodules on Shep- 

 herdia argentea in northern Minnesota. 



