140 PRINCIPLES OF SOIL MICROBIOLOGY 



spaces. An organism belonging to the mycobacteria (My cob. rubia- 

 cearum) was isolated 179 from the leaf nodules. The same organism was 

 also isolated from Pavetta and other plants. Miehe 180 isolated a rod- 

 shaped organism, Bac. foliicola, active in forming nodules on the leaves 

 of Ardisia. It is a motile rod (1-2.5 by 0.4-0.5ju) with peritrichic fiagella 

 and later changes into a branching form. These "bacteroids" may be 

 found in the cells of the leaves and also on special media. The bacteria 

 are already present in the seeds, between the embryo and the endosperm, 

 so that the plants do not have to be inoculated anew with each new 

 growth. In this respect they are similar to the endotrophic mycorrhiza 

 of the Ericaceae which are considered elsewhere. When the young 

 plants grow, the bacteria follow the growing tip to the new parts of the 

 plant, as they develop. The bacteria are eventually found in the entire 

 plant, where they develop in masses in the intracellular spaces. With 

 the development of the fruit, the bacteria are enclosed in the embryo 

 sack and remain with the seed. Miehe concluded that Bac. foliicola 

 fixed nitrogen; he recognized this phenomenon as one of hereditary 

 symbiosis. The bacteria forming nodules on the leaves of Pavetta 

 indica and Chomelia asiatica enter the stomata of the leaf, live there and 

 fix the nitrogen from the air. The bacteria are found at all the life 

 stages of the plant, symbiosis being developed to a much greater extent 

 than in the Leguminosae and being hereditary in nature. Plants freed 

 from bacteria, by warming the seed for 25 minutes at 50°C, develop 

 very slowly and suffer from lack of nitrogen. The bacteria are aerobic, 

 rod-shaped cells. 181 



The presence of nitrogen-fixing bacteria in the swollen glands on the 

 points of the leaves of Dioscorea macroura has also been demonstrated. 182 



179 von Faber, F. C. Die Bakteriensymbiose der Rubiaceen. Jahrb. wiss. 

 Bot. 54: 243-264. 1914; also Ibid. 51: 285-295. 1912. 



180 Miehe, H. Weitere Untersuchungen liber die Bakteriensymbiose bei 

 Ardisia crispa. Jahrb. wiss. Bot. 53: 1-54. 1913; 58: 29. 1917. Ber. Bot. 

 Gesell. 29: 156. 1911; 34: 576. 1916. 



181 Rao, K. A. A preliminary account of symbiotic nitrogen fixation in non- 

 leguminous plants, with special reference to Chomelia asiatica. Agr. Jour. India, 

 18: 132-143. 1923. 



182 Orr, M. V. Nitrogen fixation in leaf glands. Notes from the Roy. Bot. 

 Gard., Edinburgh, 14: 57-72. 1924. 



