262 PEOCEEDINGS OF THE 



place. These bacteria use nitrates and ammonia as food, and 

 the nitrogen escapes as free gas. A few flowering plants, such 

 as the bird's-nest orchid, are entirely dependent on dead organic 

 material for their food. They grow under trees in soil rich in 

 humus, and their roots are invested with a web of fungus hyphae, 

 Mycorhiza, which invades the root tissues. The fungus utilises 

 the carbonaceous and nitrogenous compounds in the soil, and the 

 cells of the host plant derive nourishment by digesting the 

 fungus. Some plants, such as the orchids and Ericaceae, are 

 partial saprophj^tes, and have a mycorhiza, although they are 

 apparently autotrophic. The germination of many orchid seeds 

 is impossible unless the seedling is infected by the fungus. Some- 

 times the fungus is specific to the orchid, and sometimes the same 

 fungus is capable of successfully inoculating various species. In 

 some cells the fungus grows vigorously, while in others it is digested, 

 thus passing on to its host the nourishment derived from the 

 humus. There is no evidence that the fungus can fix the nitro- 

 gen of the air. Dr. M. C. Eayner has worked out the relation- 

 ship between the common ling and the fungus which is associated 

 with it. In this case infection does not depend on the presence 

 of the fungus in the soil, but the hyphae permeate the whole 

 plant and are associated with the seed in the fruit. The plant 

 is in effect a phanerogamic lichen ! Dr. Eayner succeeded in 

 isolating the mycorhizal fungus from seeds and pieces of ovary 

 tissue. The fungus thus obtained was used for the inoculation 

 of sterile seedlings, which at once developed a root system and 

 grew vigorously under aseptic conditions in closed tubes. A 

 number of other Ericaceae were examined, and in every case 

 mycelium could be identified in the ovary of the unopened 

 flower. It was not found possible to replace the stimulus to 

 development which follows seedling infection by supplies of 

 various organic nitrogenous substances in the food material. 



The address was illustrated by a series of diagrams, etc., pro- 

 jected on the screen, as well as by a number of micro-slides showing 

 the fungal infection in roots ; it was listened to with great 

 attention, and a very hearty vote of thanks was accorded the 

 President. 



At the 559th Ordinary Meeting of the Club, held on March 8th, 

 the President, Dr. A. B. Kendle, M.A., F.R.S., in the chair, the 



