94 SYMBIOSIS. 



(2) On chlorophyllous plants. 



Frank has extended Kaininski's theory to include the 

 myntrhiza of trees and other green plants. This assumption 

 is founded on his observations of the common occurrence of 

 mycorhiza on the Cupuliferae, and many other plants. He says 

 that all trees are probably capable, under certain conditions, 

 of entering into symbiosis with mycorhiza-fungi, and that in 

 this way the tree is supplied not only with the necessary water 

 and mineral food-constituents from the soil, but also with organic 

 material derived directly from humus and decaying plant-remains. 

 The tree is thus enabled, through the mycorhiza, to directly utilize 

 organic vegetable remains. Frank supported this theory by 

 anatomical investigation of the mycorhiza of numerous plants 

 and later by physiological experiments. The latter consist in the 

 comparative cultivation of seedling forest-trees in a sterilized 

 humus-soil, and also in a non-sterilized soil containing the 

 mycorhiza-fungi. These experiments showed, in the case of 

 beech, that those trees in sterilized soil with normal roots and 

 root-hairs without mycorhiza, were poorly developed, and died 

 after several years, while the others with mycorhiza grew 

 vigorously. 



Frank also pointed out that mycorhiza are developed only 

 in soils containing humus, and in the humus layer. He 

 assumes that the fungus conveys to the tree-roots not only 

 carbon compounds, but also, since the mycorhiza-cells contain 

 no nitric acid, nitrogen in organic compounds. 



The mycorhiza-caps suppress the formation of root-hairs, but 

 I have frequently seen hairs on neighbouring roots or on parts 

 of the same root behind the fungus-cap (Figs. 17 and 18). In 

 soil free from humus, root-hairs are always present and carry 

 on their work normally. Schlicht 1 found that pines growing 

 in poor sandy soil without humus had no mycorhiza, but only 

 normal root-hairs. Keess found that pines near Erlangen had 

 quite as many rootlets without mycorhiza as with. It would 

 thus appear that while every tree possesses a number of roots 

 with fungus on them, yet the complete transformation of the 

 whole root-system to mycorhiza is by no means so general as 



t, Inaug. Dissertation, Berlin, 1889, p. 9. 

 Frank, Ber. d. deutsch. botan. Ges., 1892, p. 583. 

 lleess, Ber. d. deutsch. botan. Ges., 1885, p. 295. 



