Kelley — 106 — Mycotrophy 



Casuarina nodules from coral islands in the bay of Batavia, and said 

 that in section it is seen the nodules possess a small central strand while 

 larger or smaller groups of cortical cells are filled with protein-reacting 

 bodies resembling leguminous bacteroids. Kamerling supposed that 

 the nodules were responsible for N-fixation, and the same function 

 was ascribed to them by Adinarayana (1924), Mowry (1933), and 

 Narashimhan (1918), the last isolating bacteria that fixed N. 

 MiEHE (1918) tacitly inferred the same function, and asserted that 

 these nodules are mycodomatia, the symbiont being a small hyphal 

 fungus which heavily infests the cortex, passing directly from cell to 

 cell but never invading the vascular bundles. 



Myrica: — Brunchorst in 1887 had mentioned tubercles in M. 

 Gale which were described by Bottomley (1912) as modified lateral 

 roots. Three branches arise from the end of each primary nodule and 

 afterwards the stele grows out through the apex of the nodule into a 

 hair-like root. In each mature nodule four regions may be recognized, 

 vis.: apical meristem, "infection thread" area, "bacterial zone" which 

 includes most of the cortex, and basal zone devoid of bacteria but 

 with the cells containing oil drops. At maturity the bacteria disappear 

 and basal zone encroaches until it finally replaces all the others. In 

 old nodules, filling a majority of cortical cells and sometimes the base 

 of young nodules, mycorrhizal fungi are found. Fungal hyphae, said 

 Bottomley, were earlier thought to be responsible for nodule forma- 

 tion and it is possible that they may be of mycorrhizal nature and of 

 benefit to- the Myrica plant. Bottomley caused nodules to develop 

 by inoculation; he also showed fixation of free N. Schaede (1938) 

 considered the causal organism of this Myrica to be Actinomyces and 

 he gives a well illustrated account of the infection. 



In M. rubra, Shibata (1902) found the "fungus" (which he 

 believed to be Actinomyces) confined to a definite "ring" in the cortex. 

 In M. carolinensis, the author found beneath a cuticularized epidermis 

 a cortex of 10-11 layers of rounded cells, larger internally and full of 

 protoplasmic content. A zone of 2-3 layers commencing about the 

 fourth from the outside of cortex is a "bacterial layer" containing 

 comparatively large "rods" which are densely clustered and deeply 

 stained. About the outside of the domatium there is more or less a 

 weft of branched septate and geniculate hyphae, dark in colour. It is 

 difficult to demonstrate infection but neverheless in the outer cortex 

 there is the appearance of intracellular hyphae ; while many of the 

 cells have content suggestive of partially digested protoplasm which 

 takes a reddish stain while the bacteria stain blue. The latter divide 

 transversely to form rosettes. Under oil immersion, strands can be 



