SUPPLEMENT 79 



239, 11. 26-37, for Finally, we may note . . . same kind, read If we 

 describe the association of Leguminosae with nodule-bacteria as a case of 

 symbiosis, then, looking backwards, we may apply the term ' symbiosis ' to 

 the relationships that exist between Clostridium pasteurianum and the two 

 associated Bacteria, and we may take this opportunity of drawing attention to 

 some other cases of the same kind. 



1- 53. f or 1896 read 1906 



240, 11. 10-23, for More recently . . . this relation, read From Podocarpus 

 to the so-called Mycorhiza is only a step. We understand by the term ' My- 

 corhiza ' a symbiotic union of fungus and phanerogamic root, widely distributed 

 in nature. 



1. 35, after host read (details will be found in GALLAUD, 1906). 

 1. 52, for digested read digestive 



241, 11. 5-28, for Since the assimilation . . . (STAHL, 1900). read In this 

 way the Conifer succeeds in obtaining nitrogen, and FRANK has suggested that 

 B. radicicola and the bacteroids are also similarly digested by the Leguminosae. 

 HILTNER (comp. LAFAR, III) alone denies the digestion process both in Podo- 

 carpus and by the bacteroids. At least, so long as the fungus continues to 

 combine nitrogen it cannot be digested ; only when the higher plant, being 

 supplied with combined nitrogen, is rendered sufficiently vigorous, is it able to 

 rid itself of the fungus by digesting it. Whatever the nature of the final answer 

 may be to this problem, it is at least probable, after the behaviour of Podocarpus, 

 that other endotrophic mycorhizae are also capable of combining nitrogen. 



There are several experiments which tend to confirm this conception. 

 Thus TERNETZ (1904) has stated that a fungus isolated from heather soil has 

 the same power of combining nitrogen as that possessed by the mycorhiza- 

 fungus of Ericaceae. Still, its identity has not as yet been proved, and the 

 power of nitrogen -combination is not very evident. MULLER'S (1903) observa- 

 tions, which tend to show that the spruce can thrive in sandy soils, poor in 

 nitrogen, only when it is cultivated in company with the mountain pine, would 

 appear to support the view that the mycorhiza of the latter can combine nitro- 

 gen ; still, MULLER'S (1906) researches do not provide us with any proof of this. 

 Further, BEIJERINCK'S (1907) brief note suggests that the fungus isolated from 

 Orchidaceae is also incapable of combining free nitrogen. 



Under these circumstances it must be noted specially that there can be no 

 doubt as to the utility of the endotrophic mycorhiza in many plants, if it be 

 associated perhaps with metabolic processes other than nitrogen-combination. 

 Thus N. BERNARD (1904, 1905) has shown that endotrophic Fungi are quite 

 essential to orchids. Many seeds as a rule do not begin to germinate until 

 they have been infected with the fungus, and in other species infection of the 

 seedling must take place at earlier or later stages, otherwise development 

 ceases. Further, it would be incorrect to suppose that the relation between 

 the fungus and the flowering plant is to be interpreted generally in the sense 

 that the duty of the latter is to provide carbohydrate, and of the former to 

 collect nitrogen. Plants like Neottia, which exhibit no C-assimilation worth 

 mentioning, prevent us from holding such a view ; how their nutrition is 

 carried out we do not know. 



It seems to us important to differentiate clearly between endo- and ecto- 

 trophic mycorhizae. The latter type was first discovered by KAMIENSKI (1881) 

 in Monotropa. Soon afterwards FRANK proved its very general distribution 

 among our common forest trees (Cupuliferae, Betulaceae, Coniferae). In these 

 cases the fungus usually a member of the larger Agaricinae and Tuberaceae 

 does not as a rule enter the cells of the root, but forms a densely woven envelope 

 over the root, not even excepting the growing point. Individual fungal cells 



