Lecture VIII — 105 — Mycodomatia 



Podocarpus: — Nodules on Podocarpus chinensis were noted as 

 early as 1893 by Kellner, and were described in 1896 by v.Tubeuf. 

 They were examined in detail by Nobbe & Hiltner (1898), who 

 found a fungus growing throughout the root, and forming nodules 

 from within the roots, hence they concluded that the nodules or myco- 

 domatia are true endotrophic mycorrhizae. Plants were grown in 

 pure quartz sand for 5 years and watered with non-nitrogenous cul- 

 ture solution, the plants growing luxuriantly and presumably securing 

 N from the air through the mycodomatia. Later, Hiltner (1903) 

 said that N-fixation was shown for Podocarpus but not with the same 

 certainty as with Alnus. Kondo (1931) also wrote of N-relations of 

 these plants but his work is hidden in the Japanese language. 



Processes occurring within the Podocarpus mycodomatium were 

 described by Shibata (1902), who found a large hyphomycete which 

 by branching filled the whole cell : the host nucleus increased in volume 

 and assumed amoeboid form, dividing amitotically until as many as 

 8 nuclei are formed which become distributed in the cell, then becom- 

 ing amoeboid once more. When the fungus has attained its full growth 

 it is digested by the host-cell and the nuclei may then resume their 

 normal condition and divide mitotically. A proteolytic enzyme capable 

 of digesting fibrin was demonstrated in the tubercle. Shibata corro- 

 borated Magnus and Frank, that the fungus is subservient to the 

 host-cell. Hiltner (1903) said that the host-cell digests and absorbs 

 not only the plasm but the chitinous wall of the fungus ; and he also 

 noted nuclear activity in these cells. "Blasen" in Podocarpus, he said, 

 are equivalent to Janse's sporangioles, being partly formed and then 

 digested. McLuckie (1923) described nodules of P. spinidosa and 

 P. elata as of dual character. He said that these species, like other 

 species of the Podocarpineae, are actively engaged in N-fixation by 

 virtue of bacteria present in cortical cells. The nodules are modified 

 lateral roots and arise from the pericycle, their normal growth being 

 checked before they emerge from the cortex of the main root. Root- 

 hairs, he said, are commonly present. Nodules and cortex of main 

 root frequently contain fungal hyphae and peculiar spore-like bodies 

 belonging to the fungus ; the surface of the nodule and main root is 

 frequently invested with a loose tangle of fungal hyphae, some of 

 which enter the root tissues. The nodules of P. chinensis and P. nubi- 

 gena are occupied by a fungus (Schaede, 1943) which is considered 

 a harmless parasite since it has so slight a connection with the soil ; 

 but the arbuscular structure is markedly developed. 



Gasuarina: — Nodules filled with a gummy mass were found by 

 Janse (1897) on C. muricata in Java. Kamerling (1911) described 



